qml: control bar delayed calculation should be done at appropriate time

The calculation is not necessary, when `when` is not set. So, there is
no need to do the calculation.

At the same time, the calculation must be done _after_ `when` is set.
Currently, there is no guarantee for that and it causes issues with
expanding items getting invisible unexpectedly.

modules/gui/qt/player/qml/ControlRepeater.qml

@@ -65,8 +65,22 @@ Repeater {
 
         Binding on visible {
             delayed: true // this is important
-            when: (loader.status === Loader.Ready)
-            value: (loader.x + loader.Layout.minimumWidth <= repeater.availableWidth)
+            when: condition
+            value: {
+                if (condition)
+                    return (loader.x + loader.Layout.minimumWidth <= repeater.availableWidth)
+                else
+                    return true;
+            }
+
+            property bool condition: false
+
+            Binding on condition {
+                delayed: true
+                value: (loader.status === Loader.Ready) &&
+                       (loader.Layout.minimumWidth > 0) &&
+                       (repeater.availableWidth < Number.MAX_VALUE)
+            }
         }
 
         // Events