Don't bypass empty visibility recovery due to migration

In some situations, loading a project in 8.0 would wipe the
object visibility settings but the local settings also
require a format migration.  The migrator was adding visibility
for the shapes layer in this situation, bypassing the recovery
from having no objects visible.

common/project/project_local_settings.cpp

@@ -83,7 +83,7 @@ PROJECT_LOCAL_SETTINGS::PROJECT_LOCAL_SETTINGS( PROJECT* aProject, const wxStrin
             {
                 if( !aVal.is_array() || aVal.empty() )
                 {
-                    m_VisibleItems = GAL_SET::DefaultVisible();
+                    m_VisibleItems |= UserVisbilityLayers();
                     return;
                 }
 
@@ -439,7 +439,7 @@ PROJECT_LOCAL_SETTINGS::PROJECT_LOCAL_SETTINGS( PROJECT* aProject, const wxStrin
 
                 if( Contains( ptr ) )
                 {
-                    if( At( ptr ).is_array() )
+                    if( At( ptr ).is_array() && !At( ptr ).empty() )
                         At( ptr ).push_back( LAYER_FILLED_SHAPES - GAL_LAYER_ID_START );
                     else
                         At( "board" ).erase( "visible_items" );

pcbnew/board.cpp

@@ -891,7 +891,7 @@ void BOARD::SetVisibleAlls()
 
 GAL_SET BOARD::GetVisibleElements() const
 {
-    return m_project ? m_project->GetLocalSettings().m_VisibleItems : GAL_SET().set();
+    return m_project ? m_project->GetLocalSettings().m_VisibleItems : GAL_SET::DefaultVisible();
 }