Prevent stripping preceived extensions from new proj

wxFilename automatically detects extensions based on the last "." in a
full filename.  We need to re-add the extension if it is removed.

Fixes: lp:1816862
* https://bugs.launchpad.net/kicad/+bug/1816862

kicad/prjconfig.cpp

@@ -229,6 +229,12 @@ void KICAD_MANAGER_FRAME::OnNewProject( wxCommandEvent& aEvent )
         return;
 
     wxFileName pro( dlg.GetPath() );
+
+    // wxFileName automatically extracts an extension.  But if it isn't
+    // a .pro extension, we should keep it as part of the filename
+    if( pro.GetExt().ToStdString() != ProjectFileExtension )
+        pro.SetName( pro.GetName() + wxT( "." ) + pro.GetExt() );
+
     pro.SetExt( ProjectFileExtension );     // enforce extension
 
     if( !pro.IsAbsolute() )