Fix visible room header overflow in small window

src/gui/Pages/Chat/RoomHeader.qml

@@ -18,6 +18,13 @@ Rectangle {
     HRowLayout {
         id: row
         anchors.fill: parent
+        visible: opacity > 0
+
+        // The layout overflows somehow when focusing the room pane and
+        // is visible behind it (with a transparent theme)
+        opacity: showPaneButtons && chat.roomPane.visible ? 0 : 1
+
+        Behavior on opacity { HNumberAnimation {} }
 
         HButton {
             id: goToMainPaneButton