Typos, and bug fix for new inkscape version 1.1

[heyzec]

This is the error that occurs if user is on inkscape 1.1

Inkscape 1.1 (1:1.1+202105261517+ce6663b3b7)

Traceback (most recent call last):
  File "./matter.py", line 826, in <module>
    do_install()
  File "./matter.py", line 507, in do_install
    prepare_source_dir()
  File "./matter.py", line 350, in prepare_source_dir
    convert_icon_svg2png(icon)
  File "./matter.py", line 216, in convert_icon_svg2png
    exit_code = converter(color, src_path, dst_path, whisper=whisper)
  File "/home/heyzec/Desktop/matter/matter/svg2png.py", line 86, in inkscape_convert_svg2png
    inkscape_major = re.search(r"(\d+)\.\d+\.\d+", version_string).group(1)
AttributeError: 'NoneType' object has no attribute 'group'

[mateosss]

Thanks a lot!