Filename not updated and modification time reinitialized when "save as" failed

Mousepad version: 0.4.2

Steps to reproduce: open a file and try to save it on an already existing read-only file.

The tab label then shows a wrong filename (the one selected in the "save as" dialog), and the modification time was reinitialized when it should have been kept (one has to look at the code to see that).