Fix implicitWidth

src/QmlControls/SubMenuButton.qml

@@ -7,7 +7,7 @@ import QGroundControl.Palette       1.0
 import QGroundControl.ScreenTools   1.0
 
 Button {
-    id: _rootButton
+    id:             _rootButton
     property bool   setupComplete:  true                                    ///< true: setup complete indicator shows as completed
     property bool   setupIndicator: true                                    ///< true: show setup complete indicator
     property string imageResource:  "/qmlimages/subMenuButtonImage.png"     ///< Button image
@@ -17,6 +17,7 @@ Button {
 
     checkable:      true
     implicitHeight: ScreenTools.isTinyScreen ? ScreenTools.defaultFontPixelHeight * 3.5 : ScreenTools.defaultFontPixelHeight * 2.5
+    implicitWidth:  __panel.implicitWidth
 
     style: ButtonStyle {
         id: buttonStyle