[vim mode] Fix argument of scanForBracket method call

Author: hidaiy

keymap/vim.js

@@ -3552,8 +3552,8 @@
       // cursor is on a matching open bracket.
       var offset = curChar === openSym ? 1 : 0;
 
-      start = cm.scanForBracket(Pos(cur.line, cur.ch + offset), -1, null, {'bracketRegex': bracketRegexp});
-      end = cm.scanForBracket(Pos(cur.line, cur.ch + offset), 1, null, {'bracketRegex': bracketRegexp});
+      start = cm.scanForBracket(Pos(cur.line, cur.ch + offset), -1, undefined, {'bracketRegex': bracketRegexp});
+      end = cm.scanForBracket(Pos(cur.line, cur.ch + offset), 1, undefined, {'bracketRegex': bracketRegexp});
 
       if (!start || !end) {
         return { start: cur, end: cur };