lib: Fix serializer_serialize test

I wasn't freeing the deserialized renderer, which obviously leaks a lot
of memory.
I also moved the assert to after these frees, since this test still is
still failing, and I don't want the misleading leak report from ASAN
caused by the early-return.
Come to think of it, I really should refactor test_assert() to set a
flag we always return at the end, so we don't encounter this same issue
later on. // TODO!

tests/test_serializer.h

@@ -71,12 +71,15 @@ bool serializer_serialize(void) {
 	test_assert(deserialized);
 
 	char *ser1 = serialize_renderer(deserialized);
-	test_assert(stringEquals(ser0, ser1));
+	bool match = stringEquals(ser0, ser1);
 
 	free(ser0);
 	free(ser1);
 
 	cr_destroy_renderer(ext);
+	cr_destroy_renderer((struct cr_renderer *)deserialized);
+
+	test_assert(match);
 
 	return true;
 }