trim values for search, fixes #1765

Closes #1765

Merge request studip/studip!1142

app/controllers/admin/user.php

@@ -112,8 +112,10 @@ class Admin_UserController extends AuthenticatedController
                 $this->order = $this->order == 'desc' ? 'asc' : 'desc';
             }
 
-            $request['vorname']    = $request['vorname'] ?: null;
-            $request['nachname']   = $request['nachname'] ?: null;
+            $request['username']   = $this->getStringValueFromRequest($request, 'username');
+            $request['email']      = $this->getStringValueFromRequest($request, 'email');
+            $request['vorname']    = $this->getStringValueFromRequest($request, 'vorname');
+            $request['nachname']   = $this->getStringValueFromRequest($request, 'nachname');
             $request['inaktiv']    = $inaktiv;
             $request['datafields'] = $search_datafields;
             $request['sort']       = $this->sortby;
@@ -213,6 +215,15 @@ class Admin_UserController extends AuthenticatedController
         }
     }
 
+    private function getStringValueFromRequest(array $request, string $key): ?string
+    {
+        if (!isset($request[$key])) {
+            return null;
+        }
+
+        return trim($request[$key]) ?: null;
+    }
+
     /**
      * Bulk action (delete users or send message to all)
      */