kernel32: Fix a memory leak. Found by cross referencing Andrew Talbot's list of potential memory leaks with Smatch's view of the same problem.

dlls/kernel32/resource.c

@@ -1150,6 +1150,7 @@ static struct mapping_info *create_mapping( LPCWSTR name, BOOL rw )
     }
 
     unmap_file_from_memory( mi );
+    HeapFree( GetProcessHeap(), 0, mi );
 
     return NULL;
 }