error when handling .tiff extension images.

[parks-cs-ccf]

a tiff image might not have the preparties, 'openslide.mpp-x' and 'openslide.objective-power'

float(wsi_object.properties['openslide.mpp-x'])
Traceback (most recent call last):
File "", line 1, in
File "/opt/conda/envs/pytorch_env/lib/python3.7/site-packages/openslide/init.py", line 278, in getitem
raise KeyError()
KeyError