fix: add guard against whitespace-only entries from messing up tag search

www/src/db_handler/mysql_taglist_handling.php

@@ -22,7 +22,12 @@ function _str_to_raw_taglist($taglist) {
     $split_list = explode(' ', $taglist);
 
     $split_list = array_filter($split_list, function($entry) {
-        return !preg_match('/^\s*$/', $entry);
+        if(strlen($entry) == 0)
+            return false;
+        if(preg_match('/^\s*$/', $entry))
+            return false;
+
+        return true;
     });
 
     return $split_list;