sidepanel: fix excess margin above donation box

The top margin is unnecessary when the invitations tab is not present.

Change-Id: Ic0aafdd72d3d99f3764eeac72b2efe0c11a604ed

src/app/mainview/components/SidePanel.qml

@@ -341,7 +341,7 @@ SidePanelBase {
                 Layout.fillWidth: true
                 Layout.leftMargin: 15
                 Layout.rightMargin: 15
-                Layout.topMargin: 10
+                Layout.topMargin: sidePanelTabBar.visible ? 10 : 0
 
                 visible: JamiQmlUtils.isDonationBannerVisible
             }