[cypher mode] Fix broken handling of punctuation

Closes codemirror#6872

Author: marijnh

mode/cypher/cypher.js

@@ -19,6 +19,7 @@
 
  CodeMirror.defineMode("cypher", function(config) {
  var tokenBase = function(stream/*, state*/) {
+ curPunc = null
  var ch = stream.next();
  if (ch ==='"') {
  stream.match(/^[^"]*"/);