Fix terrain streaming crash: pendingTiles data race and missing null checks

Guard pendingTiles.erase() with queueMutex in processReadyTiles and
unloadTile to prevent data race with worker threads. Add defensive null
checks in M2/WMO render and animation paths. Move cleanupUnusedModels
out of per-tile unload loop to run once after all tiles are removed.

src/rendering/m2_renderer.cpp

@@ -1318,9 +1318,11 @@ void M2Renderer::update(float deltaTime, const glm::vec3& cameraPos, const glm::
         if (animCount < 32 || numAnimThreads_ <= 1) {
             // Sequential — not enough work to justify thread overhead
             for (size_t i : boneWorkIndices) {
+                if (i >= instances.size()) continue;
                 auto& inst = instances[i];
-                const auto& mdl = models.find(inst.modelId)->second;
+                auto mdlIt = models.find(inst.modelId);
-                computeBoneMatrices(mdl, inst);
+                if (mdlIt == models.end()) continue;
+                computeBoneMatrices(mdlIt->second, inst);
             }
         } else {
             // Parallel — dispatch across worker threads
@@ -1338,9 +1340,11 @@ void M2Renderer::update(float deltaTime, const glm::vec3& cameraPos, const glm::
                     [this, &boneWorkIndices, start, end]() {
                         for (size_t j = start; j < end; ++j) {
                             size_t idx = boneWorkIndices[j];
+                            if (idx >= instances.size()) continue;
                             auto& inst = instances[idx];
-                            const auto& mdl = models.find(inst.modelId)->second;
+                            auto mdlIt = models.find(inst.modelId);
-                            computeBoneMatrices(mdl, inst);
+                            if (mdlIt == models.end()) continue;
+                            computeBoneMatrices(mdlIt->second, inst);
                         }
                     }));
                 start = end;
@@ -1354,8 +1358,11 @@ void M2Renderer::update(float deltaTime, const glm::vec3& cameraPos, const glm::
 
     // Phase 3: Particle update (sequential — uses RNG, not thread-safe)
     for (size_t idx : boneWorkIndices) {
+        if (idx >= instances.size()) continue;
         auto& instance = instances[idx];
-        const auto& model = models.find(instance.modelId)->second;
+        auto mdlIt = models.find(instance.modelId);
+        if (mdlIt == models.end()) continue;
+        const auto& model = mdlIt->second;
         if (!model.particleEmitters.empty()) {
             emitParticles(instance, model, deltaTime);
             updateParticles(instance, deltaTime);
@@ -1471,13 +1478,16 @@ void M2Renderer::render(const Camera& camera, const glm::mat4& view, const glm::
     const M2ModelGPU* currentModel = nullptr;
 
     for (const auto& entry : sortedVisible) {
+        if (entry.index >= instances.size()) continue;
         const auto& instance = instances[entry.index];
 
         // Bind VAO once per model group
         if (entry.modelId != currentModelId) {
             if (currentModel) glBindVertexArray(0);
             currentModelId = entry.modelId;
-            currentModel = &models.find(currentModelId)->second;
+            auto mdlIt = models.find(currentModelId);
+            if (mdlIt == models.end()) continue;
+            currentModel = &mdlIt->second;
             glBindVertexArray(currentModel->vao);
         }
 

src/rendering/terrain_manager.cpp

@@ -676,7 +676,10 @@ void TerrainManager::processReadyTiles() {
         if (pending) {
             TileCoord coord = pending->coord;
             finalizeTile(std::move(pending));
+            {
+                std::lock_guard<std::mutex> lock(queueMutex);
                 pendingTiles.erase(coord);
+            }
             processed++;
         }
     }
@@ -694,16 +697,22 @@ void TerrainManager::processAllReadyTiles() {
         if (pending) {
             TileCoord coord = pending->coord;
             finalizeTile(std::move(pending));
+            {
+                std::lock_guard<std::mutex> lock(queueMutex);
                 pendingTiles.erase(coord);
             }
         }
     }
+}
 
 void TerrainManager::unloadTile(int x, int y) {
     TileCoord coord = {x, y};
 
     // Also remove from pending if it was queued but not yet loaded
+    {
+        std::lock_guard<std::mutex> lock(queueMutex);
         pendingTiles.erase(coord);
+    }
 
     auto it = loadedTiles.find(coord);
     if (it == loadedTiles.end()) {
@@ -750,14 +759,6 @@ void TerrainManager::unloadTile(int x, int y) {
     }
 
     loadedTiles.erase(it);
-
-    // Clean up any models that are no longer referenced
-    if (m2Renderer) {
-        m2Renderer->cleanupUnusedModels();
-    }
-    if (wmoRenderer) {
-        wmoRenderer->cleanupUnusedModels();
-    }
 }
 
 void TerrainManager::unloadAll() {
@@ -1091,6 +1092,14 @@ void TerrainManager::streamTiles() {
     }
 
     if (!tilesToUnload.empty()) {
+        // Clean up models that lost all instances (once, after all tiles removed)
+        if (m2Renderer) {
+            m2Renderer->cleanupUnusedModels();
+        }
+        if (wmoRenderer) {
+            wmoRenderer->cleanupUnusedModels();
+        }
+
         LOG_INFO("Unloaded ", tilesToUnload.size(), " distant tiles, ",
                  loadedTiles.size(), " remain");
     }

src/rendering/wmo_renderer.cpp

@@ -852,8 +852,11 @@ void WMORenderer::render(const Camera& camera, const glm::mat4& view, const glm:
     bool doFrustumCull = frustumCulling;
 
     auto cullInstance = [&](size_t instIdx) -> InstanceDrawList {
+        if (instIdx >= instances.size()) return InstanceDrawList{};
         const auto& instance = instances[instIdx];
-        const ModelData& model = loadedModels.find(instance.modelId)->second;
+        auto mdlIt = loadedModels.find(instance.modelId);
+        if (mdlIt == loadedModels.end()) return InstanceDrawList{};
+        const ModelData& model = mdlIt->second;
 
         InstanceDrawList result;
         result.instanceIndex = instIdx;
@@ -942,8 +945,11 @@ void WMORenderer::render(const Camera& camera, const glm::mat4& view, const glm:
 
     // ── Phase 2: Sequential GL draw ────────────────────────────────
     for (const auto& dl : drawLists) {
+        if (dl.instanceIndex >= instances.size()) continue;
         const auto& instance = instances[dl.instanceIndex];
-        const ModelData& model = loadedModels.find(instance.modelId)->second;
+        auto modelIt = loadedModels.find(instance.modelId);
+        if (modelIt == loadedModels.end()) continue;
+        const ModelData& model = modelIt->second;
 
         // Occlusion query pre-pass (GL calls — must be main thread)
         if (occlusionCulling && occlusionShader && bboxVao != 0) {