Footprint editor: re-enable a internal copper layer to add/edit keep-out zones

on internal layers in footprints.

Fixes #4096
https://gitlab.com/kicad/code/kicad/issues/4096

pcbnew/footprint_edit_frame.cpp

@@ -131,13 +131,6 @@ FOOTPRINT_EDIT_FRAME::FOOTPRINT_EDIT_FRAME( KIWAY* aKiway, wxWindow* aParent,
 
     SetBoard( new BOARD() );
 
-    // Enable one internal layer, because footprints support keepout areas that
-    // can be on internal layers only (therefore on the first internal layer)
-    // This is needed to handle these keepout in internal layers only
-    GetBoard()->SetEnabledLayers( GetBoard()->GetEnabledLayers().set( In1_Cu ) );
-    GetBoard()->SetVisibleLayers( GetBoard()->GetEnabledLayers() );
-    GetBoard()->SetLayerName( In1_Cu, _( "Inner layers" ) );
-
     // In modedit, the default net clearance is not known.
     // (it depends on the actual board)
     // So we do not show the default clearance, by setting it to 0
@@ -167,6 +160,17 @@ FOOTPRINT_EDIT_FRAME::FOOTPRINT_EDIT_FRAME( KIWAY* aKiway, wxWindow* aParent,
     // initialize parameters in m_LayersManager
     // NOTE: KifaceSettings() will return PCBNEW_SETTINGS if we started from pcbnew
     LoadSettings( GetSettings() );
+
+    // Must be set after calling LoadSettings() to be sure these parameters are
+    // non dependent on what is read in stored settings.
+    // Enable one internal layer, because footprints support keepout areas that
+    // can be on internal layers only (therefore on the first internal layer)
+    // This is needed to handle these keepout in internal layers only
+    GetBoard()->SetCopperLayerCount( 3 );
+    GetBoard()->SetEnabledLayers( GetBoard()->GetEnabledLayers().set( In1_Cu ) );
+    GetBoard()->SetVisibleLayers( GetBoard()->GetEnabledLayers() );
+    GetBoard()->SetLayerName( In1_Cu, _( "Inner layers" ) );
+
     GetGalDisplayOptions().m_axesEnabled = true;
 
     SetScreen( new PCB_SCREEN( GetPageSettings().GetSizeIU() ) );