In the example file, metadata extraction with identify fails, cf. "IWH_Blau.tif (0 × 0 pixels, file size: 21, MIME type: image/tiff, 0 pages)", and thumbs are not generated.
Another example with paged TIFF: https://commons.wikimedia.org/wiki/File:Broglie_-_Souvenirs,_1830-1832.tif
thedj[work]> Nemo_bis: that might be a bug. we use identify to get some metadata about the file i believe and it seems that the warnings make it fail. It should ignore the warnings though.