All numbers in Progress section showing as "NaN" for some catalogs

[Navino Evans]

In some Mix n' Match catalogues, the counts and % progress indicators on the catalog's overview page all read "NaN", and a message shows indicating Mix'nMatch thinks the catalog is empty.

Note: the catalogs appear to function correctly in all other ways.

This was noticed after importing catalog 1225 using the mix'n'match import page.

The fhe full list is below:

• https://tools.wmflabs.org/mix-n-match/#/catalog/1191
• https://tools.wmflabs.org/mix-n-match/#/catalog/1195
• https://tools.wmflabs.org/mix-n-match/#/catalog/1221
• https://tools.wmflabs.org/mix-n-match/#/catalog/1222
• https://tools.wmflabs.org/mix-n-match/#/catalog/1225

I can't find anything special common to all of the problem catalogs, except use of lots of special chracters in the "title" of each entry in the catalog.

This catalog also show the same problem, but appears to be completely empty (unlike those listed above): https://tools.wmflabs.org/mix-n-match/#/catalog/1186