The code seems to be doing:
g_autofree gchar *data = NULL; gsize data_len;
if (g_file_get_contents (cache_fn, &data, &data_len, &local_error) && gs_plugin_snap_set_app_pixbuf_from_data (app, data, data_len, &local_error))
And entering gs_plugin_snap_set_app_pixbuf_from_data with data set to NULL.
That suggests that g_file_get_contents has returned TRUE but set data to NULL.
The code seems to be doing:
g_autofree gchar *data = NULL;
gsize data_len;
if (g_file_ get_contents (cache_fn, &data, &data_len, &local_error) && plugin_ snap_set_ app_pixbuf_ from_data (app, data, data_len, &local_error))
gs_
And entering gs_plugin_ snap_set_ app_pixbuf_ from_data with data set to NULL.
That suggests that g_file_get_contents has returned TRUE but set data to NULL.