Fix bug when font is from a .ttc file

When a font is from a .ttc file (true type collection) and one of file's fonts has been used before for saving an xcf file, when loading that same file, or another which happened to include text written in on the of the file's fonts, the desired font might not be loaded, due to the hashes being the same for all fonts from the file.

Because all fonts from iosevka-extrabold.ttc share the same hash, after saving and loading, all text is detected as being in Iosevka Extrabold, which happens to be the first font matched with the same hash

A solution is not to use the hash at first.