Minor memory safety fixes

Core/MemMap.cpp

@@ -496,7 +496,7 @@ void Memset(const u32 _Address, const u8 _iValue, const u32 _iLength, const char
 		// TODO: This mainly seems to be produced by GPUCommon::PerformMemorySet, called from
 		// Replace_memset_jak(). Strangely, this managed to crash in Write_U8().
 		for (size_t i = 0; i < _iLength; i++) {
-			if (Memory::IsValidAddress(_Address + i)) {
+			if (Memory::IsValidAddress(_Address + (u32)i)) {
 				WriteUnchecked_U8(_iValue, (u32)(_Address + i));
 			}
 		}