Fixed crash on Linux on startup

src/slic3r/GUI/Tab.cpp

@@ -298,6 +298,7 @@ void Tab::create_preset_tab()
     // so that the cursor jumps to the last item.
     m_treectrl->Bind(wxEVT_TREE_SEL_CHANGED, [this](wxTreeEvent&) {
             if (!m_disable_tree_sel_changed_event && !m_pages.empty()) {
+#ifdef WIN32		    
                 if (m_page_switch_running)
                     m_page_switch_planned = true;
                 else {
@@ -308,6 +309,10 @@ void Tab::create_preset_tab()
                     } while (this->tree_sel_change_delayed());
                     m_page_switch_running = false;
                 }
+#else
+                // Crashes on Linux on start-up without CallAfter.
+                this->CallAfter([this]() { this->tree_sel_change_delayed(); });
+#endif
             }
         });
 
@@ -3389,7 +3394,6 @@ void Tab::activate_selected_page(std::function<void()> throw_if_canceled)
 
 bool Tab::tree_sel_change_delayed()
 {
-#if 1
     // There is a bug related to Ubuntu overlay scrollbars, see https://github.com/prusa3d/PrusaSlicer/issues/898 and https://github.com/prusa3d/PrusaSlicer/issues/952.
     // The issue apparently manifests when Show()ing a window with overlay scrollbars while the UI is frozen. For this reason,
     // we will Thaw the UI prematurely on Linux. This means destroing the no_updates object prematurely.
@@ -3403,7 +3407,6 @@ bool Tab::tree_sel_change_delayed()
 //#ifdef __WXOSX__  // Use Freeze/Thaw to avoid flickering during clear/activate new page
     wxWindowUpdateLocker noUpdates(this);
 //#endif
-#endif
 #endif
 
     Page* page = nullptr;