StringDB not working with non-human data anymore

[djwetstede]

Describe the bug
The StringDB annotator used to be able to work with non-human data, but since recently it only returns the error 'UserWarning: There is no interaction between your input list based on StringDB.', even when using data that used to work before.

To Reproduce
These are the identifiers I used to test the annotator.
ENSMUSG00000067274 - (rplp0)
ENSMUSG00000003429 - (rps11)
ENSMUSG00000000740 - (rpl13)
ENSMUSG00000017548 - (rpl19)

Then regularly call the function:
ppi_df, ppi_metadata = stringdb.get_ppi(bridgedb_df=bridgedb_df, species="Mouse")

This will produce the error mentioned above, even though when viewed in the online String database, there should be ppi's here.