Merge branch 'stable-3.1' into 'stable-3.1'

fixed typo

See merge request ispconfig/ispconfig3!909

Author: Till Brehm

interface/web/dns/dns_dkim_edit.php

@@ -128,7 +128,7 @@ function onSubmit() {
 		// check for duplicate entry
 		$check=$app->db->queryOneRecord("SELECT * FROM dns_rr WHERE zone = ? AND type = ? AND data = ? AND name = ?", $this->dataRecord["zone"], $this->dataRecord["type"], $this->dataRecord["data"], $this->dataRecord['name']);
 		if ($check!='') $app->tform->errorMessage .= $app->tform->wordbook["record_exists_txt"];
-		if (empty($this->dataRecord['data'])) $app->tform->errorMessage /= $app->tform->wordbook["dkim_disabled_txt"];
+		if (empty($this->dataRecord['data'])) $app->tform->errorMessage .= $app->tform->wordbook["dkim_disabled_txt"];
 
 		// validate selector and public-key
 		if (empty($this->dataRecord['selector'])) $app->tform->errorMessage .= '<br/>'.$app->tform->wordbook["dkim_selector_empty_txt"].'<br/>';