Fix bug #67151: strtr with empty array crashes

Author: nikic

NEWS

@@ -9,6 +9,7 @@ PHP                                                                        NEWS
     match). (Bob)
   . Fixed bug #67091 (make install fails to install libphp5.so on FreeBSD 10.0).
     (Ferenc)
+  . Fixed bug #67151 (strtr with empty array crashes). (Nikita)
 
 - CLI server:
   . Implemented FR #67429 (CLI server is missing some new HTTP response codes).

ext/standard/string.c

@@ -3155,6 +3155,10 @@ static void php_strtr_array(zval *return_value, char *str, int slen, HashTable *
 	int			patterns_len;
 	zend_llist	*allocs;
 
+	if (zend_hash_num_elements(pats) == 0) {
+		RETURN_STRINGL(str, slen, 1);
+	}
+
 	S(&text) = str;
 	L(&text) = slen;