[apps] Don't forget to call viewWillAppear

At the moment ViewController::viewWillAppear doesn't do anything, so
there is no real impact. But if we want to use it it needs to be called
from subclasses.

apps/shared/zoom_parameter_controller.cpp

@@ -55,6 +55,7 @@ bool ZoomParameterController::handleEvent(Ion::Events::Event event) {
 }
 
 void ZoomParameterController::viewWillAppear() {
+  ViewController::viewWillAppear();
   m_contentView.curveView()->setOkView(nullptr);
   /* We need to change the curve range to keep the same visual aspect of the
    * view. */