[xml mode] Fix crash when tagName is null

Author: marijnh

mode/xml/xml.js

@@ -187,6 +187,10 @@ CodeMirror.defineMode("xml", function(editorConf, config_) {
     };
   }
 
+  function lower(tagName) {
+    return tagName && tagName.toLowerCase();
+  }
+
   function Context(state, tagName, startOfLine) {
     this.prev = state.context;
     this.tagName = tagName || "";
@@ -205,8 +209,8 @@ CodeMirror.defineMode("xml", function(editorConf, config_) {
         return;
       }
       parentTagName = state.context.tagName;
-      if (!config.contextGrabbers.hasOwnProperty(parentTagName.toLowerCase()) ||
-          !config.contextGrabbers[parentTagName.toLowerCase()].hasOwnProperty(nextTagName.toLowerCase())) {
+      if (!config.contextGrabbers.hasOwnProperty(lower(parentTagName)) ||
+          !config.contextGrabbers[lower(parentTagName)].hasOwnProperty(lower(nextTagName))) {
         return;
       }
       popContext(state);
@@ -240,7 +244,7 @@ CodeMirror.defineMode("xml", function(editorConf, config_) {
     if (type == "word") {
       var tagName = stream.current();
       if (state.context && state.context.tagName != tagName &&
-          config.implicitlyClosed.hasOwnProperty(state.context.tagName.toLowerCase()))
+          config.implicitlyClosed.hasOwnProperty(lower(state.context.tagName)))
         popContext(state);
       if ((state.context && state.context.tagName == tagName) || config.matchClosing === false) {
         setStyle = "tag";
@@ -279,7 +283,7 @@ CodeMirror.defineMode("xml", function(editorConf, config_) {
       var tagName = state.tagName, tagStart = state.tagStart;
       state.tagName = state.tagStart = null;
       if (type == "selfcloseTag" ||
-          config.autoSelfClosers.hasOwnProperty(tagName.toLowerCase())) {
+          config.autoSelfClosers.hasOwnProperty(lower(tagName))) {
         maybePopContext(state, tagName);
       } else {
         maybePopContext(state, tagName);
@@ -359,16 +363,16 @@ CodeMirror.defineMode("xml", function(editorConf, config_) {
           if (context.tagName == tagAfter[2]) {
             context = context.prev;
             break;
-          } else if (config.implicitlyClosed.hasOwnProperty(context.tagName.toLowerCase())) {
+          } else if (config.implicitlyClosed.hasOwnProperty(lower(context.tagName))) {
             context = context.prev;
           } else {
             break;
           }
         }
       } else if (tagAfter) { // Opening tag spotted
         while (context) {
-          var grabbers = config.contextGrabbers[context.tagName.toLowerCase()];
-          if (grabbers && grabbers.hasOwnProperty(tagAfter[2].toLowerCase()))
+          var grabbers = config.contextGrabbers[lower(context.tagName)];
+          if (grabbers && grabbers.hasOwnProperty(lower(tagAfter[2])))
             context = context.prev;
           else
             break;