EDIT: Open fit files with Rice compression from Siril

[chges100]

OS: Ubuntu Linux 20.04 Program version: v0.0.5

When loading a 32bit floating point .fit file exported with Siril, the following exception is thrown:

Exception in Tkinter callback Traceback (most recent call last): File "tkinter/init.py", line 1892, in call File "gui.py", line 236, in menu_open_clicked File "gui.py", line 307, in set_image AttributeError: 'NoneType' object has no attribute 'shape'

Happens with 16-bit fit files from Siril, too.