SUMMARY
In Rectangular Region mode, right-clicking on the screen area when there's no active selection should Cancel the Rectangle Region mode as if Esc were pressed.


STEPS TO REPRODUCE
1. Open Spectacle
2. Select "Rectangular Region"
3. Right-click on the darkened area of the screen when there's no active selection

OBSERVED RESULT
It does nothing.

EXPECTED RESULT
It should cancel the Rectangular Region mode as if Esc were pressed, similar to how right-clicking dismisses the active selection.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 5.27.7
KDE Frameworks Version: 5.110.0
Qt Version: 5.15.10

ADDITIONAL INFORMATION
The suggested behavior can be seen in Snipaste(https://www.snipaste.com/).