ZP-1271 Overwrite user only if no specific username was requested.

Released under the Affero GNU General Public License (AGPL) version 3.

src/backend/kopano/kopano.php

@@ -1514,9 +1514,9 @@ class BackendKopano implements IBackend, ISearchProvider {
         list($user, $domain) = Utils::SplitDomainUser($store);
         if ($user === false) {
             $user = $this->mainUser;
-        }
-        if ($this->impersonateUser) {
-            $user = $this->impersonateUser;
+            if ($this->impersonateUser) {
+                $user = $this->impersonateUser;
+            }
         }
 
         // if there is a ReplyBackImExporter, the exporter needs to run!