Fix minor safety and visibility issues

Move onUpdateUI from public to private in EDA_BASE_FRAME since
it is an internal event handler bound via Bind(), not part of
the public API.

Capture the empty-check result before erasing rows in
library_manager.cpp to avoid using invalidated iterators from
the subrange returned by std::ranges::remove_if.

Add null guards to the netHighlightCond toolbar condition
lambda in PCB_EDIT_FRAME to prevent null dereference during
shutdown, matching the pattern used by other toolbar
conditions fixed in f962de966b.

common/libraries/library_manager.cpp

@@ -479,9 +479,10 @@ void LIBRARY_MANAGER::LoadGlobalTables( std::initializer_list<LIBRARY_TABLE_TYPE
                                    && !wxFileName::Exists( path );
                         } );
 
+                bool hadRemovals = !toErase.empty();
                 table->Rows().erase( toErase.begin(), toErase.end() );
 
-                if( !toErase.empty() )
+                if( hadRemovals )
                 {
                     table->Save().map_error(
                             []( const LIBRARY_ERROR& aError )

include/eda_base_frame.h

@@ -200,8 +200,6 @@ public:
     static void HandleUpdateUIEvent( wxUpdateUIEvent& aEvent, EDA_BASE_FRAME* aFrame,
                                      ACTION_CONDITIONS aCond );
 
-    void onUpdateUI( wxUpdateUIEvent& aEvent );
-
     virtual void OnMove( wxMoveEvent& aEvent )
     {
         aEvent.Skip();
@@ -752,6 +750,8 @@ protected:
     DECLARE_EVENT_TABLE()
 
 private:
+    void onUpdateUI( wxUpdateUIEvent& aEvent );
+
     /**
      * (with its unexpected name so it does not collide with the real OnWindowClose()
      * function provided in derived classes) is called just before a window

pcbnew/pcb_edit_frame.cpp

@@ -1119,8 +1119,19 @@ void PCB_EDIT_FRAME::setupUIConditions()
     auto netHighlightCond =
             [this]( const SELECTION& )
             {
-                KIGFX::RENDER_SETTINGS* settings = GetCanvas()->GetView()->GetPainter()->GetSettings();
-                return !settings->GetHighlightNetCodes().empty();
+                if( auto* canvas = GetCanvas() )
+                {
+                    if( auto* view = canvas->GetView() )
+                    {
+                        if( auto* painter = view->GetPainter() )
+                        {
+                            if( auto* settings = painter->GetSettings() )
+                                return !settings->GetHighlightNetCodes().empty();
+                        }
+                    }
+                }
+
+                return false;
             };
 
     auto enableNetHighlightCond =