fix empty array result on user search

Signed-off-by: dartcafe <github@dartcafe.de>

lib/Service/SystemService.php

@@ -121,11 +121,14 @@ class SystemService {
 		$list = [];
 		if ($query !== '') {
 			preg_match_all(self::REGEX_PARSE_MAIL, $query, $parsedQuery);
+
+			if (!empty($parsedQuery[1]) && !empty($parsedQuery[2])) {
 				$emailAddress = $parsedQuery[2][0];
 				$displayName = $parsedQuery[1][0];
 				if ($emailAddress && self::isValidEmail($emailAddress)) {
 					$list[] = new Email($emailAddress, $displayName, $emailAddress);
 				}
+			}
 
 			$list = array_merge($list, UserBase::search($query));
 		}