#5893: Fix crash after resizing the client side buffers, seems like o…

…penGL is accessing the vertex data after the old buffer has gone out of business.

libs/render/ContinuousBuffer.h

@@ -29,6 +29,7 @@ class ContinuousBuffer
     static constexpr std::size_t GrowthRate = 1; // 100% growth each time
 
     std::vector<ElementType> _buffer;
+    std::vector<ElementType> _inactiveBuffer;
 
     struct SlotInfo
     {
@@ -212,7 +213,13 @@ class ContinuousBuffer
 
         // Allocate more memory
         auto additionalSize = std::max(_buffer.size() * GrowthRate, requiredSize);
-        _buffer.resize(_buffer.size() + additionalSize);
+        auto newSize = _buffer.size() + additionalSize;
+
+        // Park the old data in the inactive buffer, some GL thread might still access it
+        _inactiveBuffer = std::move(_buffer);
+
+        _buffer = _inactiveBuffer;
+        _buffer.resize(newSize);
 
         // Use the right most slot for our requirement, then cut up the rest of the space
         auto& rightmostFreeSlot = _slots[rightmostFreeSlotIndex];