facebook-api: use the icon URL as a backup checksum

There is a report of the 'oh' parameter missing from some of the icon
images, which is used as the checksum. The solution is to simply use
the URL itself as the checksum in the *rare* case the 'oh' parameter
is missing.

facebook/facebook-api.c

@@ -1936,9 +1936,14 @@ fb_api_cb_contact(FbHttpRequest *req, gpointer data)
 
     prms = fb_http_values_new();
     fb_http_values_parse(prms, user.icon, TRUE);
-    user.csum = fb_http_values_dup_str(prms, "oh", &err);
+    user.csum = fb_http_values_dup_str(prms, "oh", NULL);
     fb_http_values_free(prms);
 
+    if (G_UNLIKELY(user.csum == NULL)) {
+        /* Revert to the icon URL as the unique checksum */
+        user.csum = g_strdup(user.icon);
+    }
+
     g_signal_emit_by_name(api, "contact", &user);
     fb_api_user_reset(&user, TRUE);
     g_object_unref(values);
@@ -2016,8 +2021,14 @@ fb_api_cb_contacts(FbHttpRequest *req, gpointer data)
 
         prms = fb_http_values_new();
         fb_http_values_parse(prms, user->icon, TRUE);
-        user->csum = fb_http_values_dup_str(prms, "oh", &err);
+        user->csum = fb_http_values_dup_str(prms, "oh", NULL);
         fb_http_values_free(prms);
+
+        if (G_UNLIKELY(user->csum == NULL)) {
+            /* Revert to the icon URL as the unique checksum */
+            user->csum = g_strdup(user->icon);
+        }
+
         users = g_slist_prepend(users, user);
     }