Update schematic when saving tuned value

Also avoids a known(!) crash when the existing item has been deleted
while tuning.

Fixes https://gitlab.com/kicad/code/kicad/issues/9502

eeschema/sim/sim_plot_frame.cpp

@@ -572,6 +572,22 @@ void SIM_PLOT_FRAME::AddTuner( SCH_SYMBOL* aSymbol )
     }
 }
 
+void SIM_PLOT_FRAME::UpdateTunerValue( SCH_SYMBOL* aSymbol, const wxString& aValue )
+{
+    for( auto& item : m_schematicFrame->GetScreen()->Items().OfType( SCH_SYMBOL_T ) )
+    {
+        if( item == aSymbol )
+        {
+            aSymbol->SetValue( aValue );
+
+            m_schematicFrame->UpdateItem( aSymbol, false, true );
+            m_schematicFrame->OnModify();
+            break;
+        }
+    }
+
+}
+
 
 void SIM_PLOT_FRAME::RemoveTuner( TUNER_SLIDER* aTuner, bool aErase )
 {

eeschema/sim/sim_plot_frame.h

@@ -109,6 +109,15 @@ public:
      */
     void RemoveTuner( TUNER_SLIDER* aTuner, bool aErase = true );
 
+    /**
+     * Safely update the value of the associated symbol without dereferencing
+     * the symbol.
+     *
+     * @param aSymbol pointer to the symbol needing updating
+     * @param aValue new value of the symbol
+     */
+    void UpdateTunerValue( SCH_SYMBOL* aSymbol, const wxString& aValue );
+
     /**
      * Return the currently opened plot panel (or NULL if there is none).
      */

eeschema/widgets/tuner_slider.cpp

@@ -185,8 +185,7 @@ void TUNER_SLIDER::onClose( wxCommandEvent& event )
 
 void TUNER_SLIDER::onSave( wxCommandEvent& event )
 {
-    /// @todo it will crash when component is removed; completely remove m_symbol
-    m_symbol->GetField( VALUE_FIELD )->SetText( m_value.ToOrigString() );
+    m_frame->UpdateTunerValue( m_symbol, m_value.ToOrigString() );
 }