fix(): singlestat init

public/app/plugins/panel/singlestat/module.ts

@@ -57,11 +57,10 @@ class SingleStatCtrl extends MetricsPanelCtrl {
     this.events.on('data-received', this.onDataReceived.bind(this));
     this.events.on('data-error', this.onDataError.bind(this));
     this.events.on('data-snapshot-load', this.onDataSnapshotLoad.bind(this));
+    this.events.on('init-edit-mode', this.onInitEditMode.bind(this));
   }
 
-  initEditMode() {
-    super.initEditMode();
-    this.icon =  "fa fa-dashboard";
+  onInitEditMode() {
     this.fontSizes = ['20%', '30%','50%','70%','80%','100%', '110%', '120%', '150%', '170%', '200%'];
     this.addEditorTab('Options', 'public/app/plugins/panel/singlestat/editor.html', 2);
     this.unitFormats = kbn.getUnitFormats();