fix error when search pattern is empty

src/Bundle/ChillPersonBundle/Repository/PersonACLAwareRepository.php

@@ -136,8 +136,11 @@ final class PersonACLAwareRepository implements PersonACLAwareRepositoryInterfac
         $andWhereSearchClause = [];
         $andWhereSearchClauseArgs = [];
 
-        if ('' !== $default) {
+        if ('' !== trim($default)) {
             foreach (explode(' ', $default) as $str) {
+                if ('' === trim($str)) {
+                    continue;
+                }
                 $pertinence[] =
                     'STRICT_WORD_SIMILARITY(LOWER(UNACCENT(?)), person.fullnamecanonical) + ' .
                     "(person.fullnamecanonical LIKE '%' || LOWER(UNACCENT(?)) || '%')::int + " .