Refer to wxPGProperty associated with wxPGComboBox editor in all drawing operations

Store wxPGProperty for which wxPGComboBox editor is activated and use
this reference in all further drawing operations instead of retrieving
each time currently selected wxPGProperty which during the entire
lifetime of the editor is the same as property selected on editor
activation.

See #18211.

src/propgrid/editors.cpp

@@ -645,10 +645,11 @@ public:
 
         // Enabling double-click processor makes sense
         // only for wxBoolProperty.
-        wxPGProperty* selProp = GetGrid()->GetSelection();
-        if (wxDynamicCast(selProp, wxBoolProperty))
+        m_selProp = GetGrid()->GetSelection();
+        wxASSERT(m_selProp);
+        if (wxDynamicCast(m_selProp, wxBoolProperty))
         {
-            m_dclickProcessor = new wxPGDoubleClickProcessor(this, selProp);
+            m_dclickProcessor = new wxPGDoubleClickProcessor(this, m_selProp);
             PushEventHandler(m_dclickProcessor);
         }
 
@@ -729,9 +730,12 @@ public:
         );
     }
 
+    wxPGProperty* GetProperty() const { return m_selProp; }
+
 private:
     wxPGDoubleClickProcessor*   m_dclickProcessor;
     bool                        m_sizeEventCalled;
+    wxPGProperty*               m_selProp;
 };
 
 
@@ -741,7 +745,8 @@ void wxPropertyGrid::OnComboItemPaint( const wxPGComboBox* pCb,
                                        wxRect& rect,
                                        int flags )
 {
-    wxPGProperty* p = GetSelection();
+    wxPGProperty* p = pCb->GetProperty();
+
     wxString text;
 
     const wxPGChoices& choices = p->GetChoices();