Hey there!
Trying to export a small level (T2U v.1.0.9.4, Unity: 2017.3.1f1) greeted me with 2 problems, which I just can't resolve:
First, I can't preview the map when I load it in Tiled2Unity, because I'm greeted with a "Index out of range" exception:

Nonetheless I tried to export, which resulted only in an .xml file being generated in the Imported folder and then the following Unity error:

("castle.png" is one of the tilesets I'm using)
A bit of context, I had an image layer before that, with a fairly big image in it. First it was complaining about that file, so I removed it just to test if that was the issue, now it's just complaining about the next file in order.
Said "castle.png" is not existing in that folder, prior to exporting (nor does it exist afterwards, as I said, I just get the .xml file).
I'm a bit stumped by this, so any suggestion would be appreciated.