Preview windows don't reflect open windows

[mcarans]

• Cinnamon version 2.6.7

• Extension version Latest

  • Ensure this issue applies to the latest version of ITM found in the Cinnamon Spices repository.

• Linux distribution Mint 18.3

• Pastbin the outputs of:

  • ~/.cinnamon/configs/IcingTaskManager@json/*.json
  • ~/.cinnamon/glass.log
  • ~/.xsession-errors https://pastebin.com/nuRWLQuY

• Describe the steps needed to be taken in order to reproduce this bug. Open and close a few windows and dialogs for the same app eg. PyCharm. Preview becomes wrong - ie. does not reflect open windows.

[jaszhix]

Let's merge this into #182 since the cause is the same.