Matlab style concatenation is incorrect and causes crashes

[tadhgmister]

yolact/layers/output_utils.py

Line 88 in 57b8f2d

scores = [scores, scores * maskiou_p]

This line takes what was initially in scores and nests it in a plain python list along with a scaled version of scores. However this variable scores is unconditionally used in eval.py as though it is a numpy array:

yolact/eval.py

Line 155 in 57b8f2d

idx = t[1].argsort(0, descending=True)[:args.top_k]

This means that any case that hits the line in layers/output_utils.py will cause the evaluation to crash with an error claiming AttributeError: 'list' object has no attribute 'argsort'

I tried just replacing this with np.concatenate but that caused a different error so I'm not totally sure what the intent is. How should this be resolved?
I forgot the extra parenthesis when I first used it, works in the PR attached.