[bug] Blank Pattern Lines with only Instrument Number

[bazz1tv]

Describe the bug
With the attached file, if track 1 has two or more trailing rows that feature only an instrument number, track 2's instrument gets forced to 1, despite being specified to use a different instrument.

Expected behavior
I have a couple ideas of what could be done
a) Interpret these lines as blank lines when processing into APU.
b) change the active instrument, retaining pitch info.

Screenshots

pmod-bugged.zip