PanelView: Skip invalid screen geometries in updateStruts

My second (internal) screen is disabled and has 0x0 size.
This fixes setting the struts for panel and correctly calculating
the available desktop area.

CCBUG: 348043

Differential Revision: https://phabricator.kde.org/D1238

shell/panelview.cpp

@@ -912,6 +912,9 @@ void PanelView::updateStruts()
             }
 
             const QRect otherScreen = corona()->screenGeometry(i);
+            if (!otherScreen.isValid()) {
+                continue;
+            }
 
             switch (location())
             {