handle self-assign (#1331)

WickedEngine/wiAllocator.h

@@ -546,6 +546,7 @@ namespace wi::allocator
 			}
 			Allocation& operator=(const Allocation& other)
 			{
+				if (&other == this) return *this;
 				Reset();
 				allocator = other.allocator;
 				internal_state = other.internal_state;

WickedEngine/wiFunction.h

@@ -86,6 +86,7 @@ namespace wi
 
 		function& operator=(const function& other)
 		{
+			if (&other == this) return *this;
 			destroy();
 			if (other.ptr)
 			{