Fixed bug in VmaDefragmentationContext_T::ComputeDefragmentation_Extensive

Fixes #328. Code by @medranSolus.

include/vk_mem_alloc.h

diff --git a/include/vk_mem_alloc.h b/include/vk_mem_alloc.h
index 9b7aa62..823cef8 100644
--- a/include/vk_mem_alloc.h
+++ b/include/vk_mem_alloc.h
@@ -13732,7 +13732,7 @@
             {
                 // Full clear performed already
                 if (prevMoveCount != m_Moves.size() && freeMetadata->GetNextAllocation(handle) == VK_NULL_HANDLE)
-                    reinterpret_cast<size_t*>(m_AlgorithmState)[index] = last;
+                    vectorState.firstFreeBlock = last;
                 return true;
             }
         }