wusa: Zero out identity on error path in read_identity.

Fixes double frees in read_components and read_dependency. The double
frees could also be fixed by using free instead of free_dependency in
those functions, but zeroing out the pointers is easier to understand
because it ensures that alloc_dependency can always be paired with
free_dependency.

programs/wusa/manifest.c

@@ -275,6 +275,7 @@ static BOOL read_identity(IXMLDOMElement *root, struct assembly_identity *identi
 
 error:
     clear_identity(identity);
+    memset(identity, 0, sizeof(*identity));
     return FALSE;
 }