decimal subframes being rounded to 0 still contain negative sign

[justinfx]

When using subframes with a number that is small enough to be rounded to zero, it can still be left with a negative sign:

fs = fileseq.FileSequence("#.#", allow_subframes=True)
fsString = fs.frame(-7.10543e-15)
# -000.0000

It would be expected that 0000.0000 would be returned here.

But is caused by the quantize() that occurs when padding the decimal:
https://github.com/justinfx/fileseq/blob/v1.15.1/src/fileseq/utils.py#L415

We should check if the value ends up being zero, and use the abs value, before string formatting.

[justinfx]

released via v1.15.2