[ticket/11051] add get_word_len() in sphinx search

get_word_len() for sphinx search backend returns false always and
triggers proper error.

PHPBB3-11051

phpBB/includes/search/fulltext_sphinx.php

@@ -108,6 +108,16 @@ class phpbb_search_fulltext_sphinx
 		return $this->search_query;
 	}
 
+	/**
+	 * Returns false as there is no word_len array
+	 *
+	 * @return false
+	 */
+	public function get_word_length()
+	{
+		return false;
+	}
+
 	/**
 	 * Returns the common_words array
 	 *