Fix for out-of-bound accessing last free block in EXTENSIVE defragmentation algorithm.
Fix for out-of-bound accessing last free block in EXTENSIVE defragmentation algorithm.

Code by @medranSolus
See #232

GPUOpen-LibrariesAndSDKs/VulkanMemoryAllocator,GPUOpen-LibrariesAndSDKs/VulkanMemoryAllocator,GPUOpen-LibrariesAndSDKs/VulkanMemoryAllocator