Pressing delete without selecting a bounding box crashes Labelimg

[TheNoodleNinja]

Pressing delete without having selected a bounding box results in LabelImg crashing instead of nothing happening.

Traceback (most recent call last):
  File "/home/<user>/miniconda3/envs/labelimg/lib/python3.8/site-packages/labelImg/labelImg.py", line 774, in shape_selection_changed
    self.shapes_to_items[shape].setSelected(True)
KeyError: <libs.shape.Shape object at 0x7f9134146bb0>
Aborted (core dumped)

• OS:Ubuntu 20.04.4 LTS
• PyQt version: 5.15.6

[nine]

This is a potential duplicate of #858