Merge branch 'fix-reset-template' into 'master'

Fix JS error when reseting new issue template

Fixes JS error when trying to reset template when no template has been set.

See merge request !7978

app/assets/javascripts/blob/template_selector.js.es6

@@ -70,6 +70,8 @@
       // e.g.
       // Api.gitignoreText item.name, @requestFileSuccess.bind(@)
       requestFileSuccess(file, { skipFocus } = {}) {
+        if (!file) return;
+
         const oldValue = this.editor.getValue();
         let newValue = file.content;