s9y#844 add another regex to avoid boolean operator alone that could lead to error

Author: GuillaumeValadas

include/functions_entries.inc.php

@@ -882,7 +882,7 @@ function &serendipity_searchEntries($term, $limit = '', $searchresults = '') {
         $cond['distinct'] = '';
         $term             = str_replace('"', '"', $term);
         $relevance_enabled = true;
-        if (preg_match('@[\+\-\*~<>\(\)"].[\S]*@', $term)) {
+        if (preg_match('@[\+\-\*~<>\(\)"].[\S]*@', $term) && preg_match('@\s*[\+\-\*~<>\(\)]\s*$@', $term) === 0 ) {
             $cond['find_part'] = "MATCH(title,body,extended) AGAINST('$term' IN BOOLEAN MODE)";
         } else {
             $cond['find_part'] = "MATCH(title,body,extended) AGAINST('$term')";