FIX: [STUDIO-2825] ctrl + tab only switch main pages

Change-Id: I10ed43929e4b757fb7c5415ba23a78ded1f2c7d0
(cherry picked from commit 10983c4d177b772e8eda264e5a9957218f779435)

src/slic3r/GUI/MainFrame.cpp

@@ -962,7 +962,6 @@ void MainFrame::init_tabpanel()
         else if (panel == m_monitor) {
             //monitor
         }
-
 #ifndef __APPLE__
         if (sel == tp3DEditor) {
             m_topbar->EnableUndoRedoItems();
@@ -972,6 +971,9 @@ void MainFrame::init_tabpanel()
         }
 #endif
 
+        if (panel)
+            panel->SetFocus();
+
         /*switch (sel) {
         case TabPosition::tpHome:
             show_option(false);