Stop misleading error when recent project doesn't exist

[GriffinRichards]

Currently, if the recent_project directory doesn't exist Porymap will try to open it anyway, and fail with an error message about the first thing it was unable to find. Right now that's the map layouts:

There was an error opening the project <project path>. Please see <log path> for full error details.

Failed to read map layouts from <project path>/data/layouts/layouts.json

Users have to close this message to open a project. Now Porymap will immediately open an empty project, and give a more helpful message in the status bar and as a warning in the log.