shell32: Fix a memory leak.

dlls/shell32/shlexec.c

@@ -1763,7 +1763,8 @@ static BOOL SHELL_execute( LPSHELLEXECUTEINFOW sei, SHELL_ExecuteW32 execfunc )
         buf = heap_alloc(size * sizeof(WCHAR));
         if (!buf || FAILED(PathCreateFromUrlW(sei_tmp.lpFile, buf, &size, 0))) {
             heap_free(buf);
-            return SE_ERR_OOM;
+            retval = SE_ERR_OOM;
+            goto end;
         }
 
         heap_free(wszApplicationName);