Fix sloppy path handling in migration for old color settings

Fixes https://gitlab.com/kicad/code/kicad/-/issues/15964

common/settings/color_settings.cpp

@@ -254,6 +254,9 @@ COLOR_SETTINGS::COLOR_SETTINGS( const wxString& aFilename, bool aAbsolutePath )
 
                 return true;
             } );
+
+    // this bump shouldn't have happened; add a no-op migration to avoid future issues
+    registerMigration( 4, 5, []() { return true; } );
 }
 
 
@@ -320,9 +323,10 @@ bool COLOR_SETTINGS::migrateSchema0to1()
         return true;
     }
 
-    wxString filename = m_filename + wxT( "_footprints" );
+    wxString filename = GetFilename().BeforeLast( '.' ) + wxT( "_footprints" );
 
     COLOR_SETTINGS* fpsettings = m_manager->AddNewColorSettings( filename );
+    fpsettings->SetLocation( GetLocation() );
 
     // Start out with a clone
     fpsettings->m_internals->CloneFrom( *m_internals );

common/settings/json_settings.cpp

@@ -109,6 +109,9 @@ JSON_SETTINGS::~JSON_SETTINGS()
 
 wxString JSON_SETTINGS::GetFullFilename() const
 {
+    if( m_filename.BeforeLast( '.' ) == getFileExt() )
+        return m_filename;
+
     return wxString( m_filename + "." + getFileExt() );
 }