[2.0.0] (Semi-edge-case) Opening with some other tools active gives traceback

[ryanbugden]

With SliceTool active:

Traceback (most recent call last):
  File "main.py", line 74, in <module>
AttributeError: type object 'SliceTool' has no attribute 'canSelectWithMarque'

[colinmford]

Yeah this is in regard to preventing the selection box, need to fix it