test: Fixed test-rotate for osx platfom

There was a bug in clutter-shader-effect. We have to set to zero new object
of type GValue before we can use it in g_value_init.

clutter/clutter-shader-effect.c

@@ -514,6 +514,7 @@ shader_uniform_new (const gchar  *name,
   retval->name = g_strdup (name);
   retval->type = G_VALUE_TYPE (value);
   retval->location = -1;
+  retval->value = (GValue){0};
 
   g_value_init (&retval->value, retval->type);
   g_value_copy (value, &retval->value);