qml: call loading changed handler on component completion in `MainViewLoader`

modules/gui/qt/maininterface/qml/MainViewLoader.qml

@@ -138,6 +138,8 @@ Loader {
 
         // NOTE: This call is useful to avoid a binding loop on currentComponent.
         currentComponentChanged.connect(_updateView)
+
+        isLoadingChanged() // in case boolean default value is `true`, currently it is not
     }
 
     onModelChanged: resetFocus()