restore availableScreenRect behavior

--when an id is sent that is not contained
at stored screens then the primary screen
geometry is used instead

app/dockcorona.cpp

@@ -316,11 +316,10 @@ QRegion DockCorona::availableScreenRegion(int id) const
 
 QRect DockCorona::availableScreenRect(int id) const
 {
-    if (!m_screenPool->knownIds().contains(id))
-        return {};
-
     const auto screens = qGuiApp->screens();
     const QScreen *screen{qGuiApp->primaryScreen()};
+
+    if (m_screenPool->knownIds().contains(id)) {
         QString scrName = m_screenPool->connector(id);
 
         foreach (auto scr, screens) {
@@ -329,6 +328,7 @@ QRect DockCorona::availableScreenRect(int id) const
                 break;
             }
         }
+    }
 
     if (!screen)
         return {};