game: process partial UPDATE_OBJECT packets when a block parse fails

Previously, if any single block in an SMSG_UPDATE_OBJECT packet failed
to parse (e.g. unusual spline flags), the entire packet was dropped and
all entities in it were lost. On busy zones with many CREATE_OBJECTs in
one packet, one bad NPC movement block would silently suppress all NPCs
that followed it in the same packet.

- parseUpdateObject: break instead of return false on block failure,
  so already-parsed blocks are returned to the caller
- handleUpdateObject: fall through to process partial data when parsing
  returns false but some blocks were successfully parsed

src/game/game_handler.cpp

@@ -7327,7 +7327,8 @@ void GameHandler::handleUpdateObject(network::Packet& packet) {
         static int updateObjErrors = 0;
         if (++updateObjErrors <= 5)
             LOG_WARNING("Failed to parse SMSG_UPDATE_OBJECT");
-        return;
+        if (data.blocks.empty()) return;
+        // Fall through: process any blocks that were successfully parsed before the failure.
     }
 
     auto extractPlayerAppearance = [&](const std::map<uint16_t, uint32_t>& fields,

src/game/world_packets.cpp

@@ -1252,11 +1252,14 @@ bool UpdateObjectParser::parse(network::Packet& packet, UpdateObjectData& data)
         if (!parseUpdateBlock(packet, block)) {
             static int parseBlockErrors = 0;
             if (++parseBlockErrors <= 5) {
-                LOG_ERROR("Failed to parse update block ", i + 1);
+                LOG_ERROR("Failed to parse update block ", i + 1, " of ", data.blockCount,
+                          " (", i, " blocks parsed successfully before failure)");
                 if (parseBlockErrors == 5)
                     LOG_ERROR("(suppressing further update block parse errors)");
             }
-            return false;
+            // Cannot reliably re-sync to the next block after a parse failure,
+            // but still return true so the blocks already parsed are processed.
+            break;
         }
 
         data.blocks.emplace_back(std::move(block));