fix empty array result on user search

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

lib/Service/SystemService.php

@@ -121,10 +121,13 @@ class SystemService {
 		$list = [];
 		if ($query !== '') {
 			preg_match_all(self::REGEX_PARSE_MAIL, $query, $parsedQuery);
-			$emailAddress = $parsedQuery[2][0];
-			$displayName = $parsedQuery[1][0];
-			if ($emailAddress && self::isValidEmail($emailAddress)) {
-				$list[] = new Email($emailAddress, $displayName, $emailAddress);
+
+			if (!empty($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));