Add nullptr check for kv delete operator

tier1/KeyValues.cpp

@@ -2805,14 +2805,20 @@ void *KeyValues::operator new( size_t iAllocSize, int nBlockUse, const char *pFi
 // Purpose: deallocator
 //-----------------------------------------------------------------------------
 void KeyValues::operator delete( void *pMem )
+{
+	if (pMem)
 	{
 		KeyValuesSystem()->FreeKeyValuesMemory(pMem);
 	}
+}
 
 void KeyValues::operator delete( void *pMem, int nBlockUse, const char *pFileName, int nLine )
+{
+	if (pMem)
 	{
 		KeyValuesSystem()->FreeKeyValuesMemory(pMem);
 	}
+}
 
 void KeyValues::UnpackIntoStructure( KeyValuesUnpackStructure const *pUnpackTable, void *pDest, size_t DestSizeInBytes )
 {