Don't block /groups requests from old clients

As with /keys, they don't seem to show the error message

https://forums.zotero.org/discussion/99879/report-id-542141482

controllers/ApiController.php

@@ -379,8 +379,9 @@ public function init($extra) {
 			require_once '../model/ToolkitVersionComparator.inc.php';
 
 			if (ToolkitVersionComparator::compare($_SERVER['HTTP_X_ZOTERO_VERSION'], "5.0.78" ) < 0
-					// Allow /keys request, since prefs didn't display proper error
-					&& strpos($this->uri, '/keys') === false) {
+					// Allow /keys and /groups requests, since prefs didn't display proper error
+					&& strpos($this->uri, '/keys') === false
+					&& strpos($this->uri, '/groups') === false) {
 				$this->e400("This version of Zotero is too old to sync. Please upgrade to a "
 					. "current version to continue syncing.", Z_ERROR_INVALID_INPUT);
 			}