#1516 An assertion when opening a workspace

[LETARTARE]

Contex t: Leap-15.6, wx-326-14, gcc-13.3.0, Cb-13626

When CB is started, if one or more projects have been deleted or moved, an assertion is generated which opens a dialog providing information: in this case ‘WorkspaceLoader::Open(const wxString& filename, wxString& Title)

So I'm proposing a patch that allows you to check the physical presence of the file beforehand

[Miguel Gimenez]

Applied in [r13630], thank you