DIALOG_SHIM: fix incorrect escape key handling.

Fixes #4304
https://gitlab.com/kicad/code/kicad/issues/4304

common/dialog_shim.cpp

@@ -511,7 +511,9 @@ void DIALOG_SHIM::OnButton( wxCommandEvent& aEvent )
 
 void DIALOG_SHIM::OnCharHook( wxKeyEvent& aEvt )
 {
-    if( m_parentFrame )
+    // Do not send WXK_ESCAPE char hook event to the parent frame
+    // It must be handled by the dialog itself
+    if( m_parentFrame && aEvt.GetKeyCode() != WXK_ESCAPE )
     {
         m_parentFrame->DispatchBehindModalDialog( aEvt );