Added addtional 'renderable' validator to check 'data-note-type' attr exists

app/assets/javascripts/files_comment_button.js

@@ -39,12 +39,13 @@
     FilesCommentButton.prototype.render = function(e) {
       var $currentTarget, buttonParentElement, lineContentElement, textFileElement;
       $currentTarget = $(e.currentTarget);
+
       buttonParentElement = this.getButtonParent($currentTarget);
-      if (!this.shouldRender(e, buttonParentElement)) {
-        return;
-      }
-      textFileElement = this.getTextFileElement($currentTarget);
+      if (!this.validateButtonParent(buttonParentElement)) return;
       lineContentElement = this.getLineContent($currentTarget);
+      if (!this.validateLineContent(lineContentElement)) return;
+
+      textFileElement = this.getTextFileElement($currentTarget);
       buttonParentElement.append(this.buildButton({
         noteableType: textFileElement.attr('data-noteable-type'),
         noteableID: textFileElement.attr('data-noteable-id'),
@@ -119,10 +120,14 @@
       return newButtonParent.is(this.getButtonParent($(e.currentTarget)));
     };
 
-    FilesCommentButton.prototype.shouldRender = function(e, buttonParentElement) {
+    FilesCommentButton.prototype.validateButtonParent = function(buttonParentElement) {
       return !buttonParentElement.hasClass(EMPTY_CELL_CLASS) && !buttonParentElement.hasClass(UNFOLDABLE_LINE_CLASS) && $(COMMENT_BUTTON_CLASS, buttonParentElement).length === 0;
     };
 
+    FilesCommentButton.prototype.validateLineContent = function(lineContentElement) {
+      return lineContentElement.attr('data-note-type') && lineContentElement.attr('data-note-type') !== '';
+    };
+
     return FilesCommentButton;
 
   })();