Make sure a project is loaded at all times

For now, much of KiCad depends on Prj() working, so when we
are asked to unload a project, immediately load the null project
so that nothing breaks.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/5374

common/settings/settings_manager.cpp

@@ -735,6 +735,10 @@ bool SETTINGS_MANAGER::UnloadProject( PROJECT* aProject, bool aSave )
 
     m_projects.erase( aProject->GetProjectFullName() );
 
+    // Immediately reload a null project; this is required until the rest of the application
+    // is refactored to not assume that Prj() always works
+    LoadProject( "" );
+
     // Remove the reference in the environment to the previous project
     wxSetEnv( PROJECT_VAR_NAME, "" );
 

kicad/kicad_manager_frame.cpp

@@ -384,10 +384,6 @@ bool KICAD_MANAGER_FRAME::CloseProject( bool aSave )
 
         m_active_project = false;
         mgr.UnloadProject( &Prj() );
-
-        // TODO(JE): Remove this if apps are refactored to not assume Prj() always works
-        // Need to create a project early for now (it can have an empty path for the moment)
-        mgr.LoadProject( "" );
     }
 
     ClearMsg();

pcbnew/files.cpp

@@ -308,9 +308,6 @@ bool PCB_EDIT_FRAME::Files_io_from_id( int id )
 
         onBoardLoaded();
 
-        // Don't set name until the user hits save, so project files are not created
-        mgr->LoadProject( "" );
-
         LoadProjectSettings();
 
         OnModify();