Draft: fix 2 edit mode issues

[Roy-043]

2 edit mode issues were fixed:

1. Double clicking a Draft object in the Tree would result in an error if the Draft WB was not loaded. Now there is a warning.
2. The introduction of Std_UserEditMode means that edit mode can be non-zero. This required a modification of the unsetEdit function.

Forum discussion about issue 1: https://forum.freecadweb.org/viewtopic.php?f=23&t=59179

@0penBrain Can you have a look at the unsetEdit function? Maybe there is a better way to do this?

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[berndhahnebach]

CI passes ... https://gitlab.com/berndhahnebach/FreeCAD/-/pipelines/376354350 and https://gitlab.com/berndhahnebach/FreeCAD/-/pipelines

[0penBrain]

@Roy-043 This looks totally good to me :)

[berndhahnebach]

Following a link to the branch on the CI-repository:

https://gitlab.com/berndhahnebach/FreeCAD/-/commits/PR_5060

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If there is no status available the PR should be rebased on latest master.
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https://gitlab.com/berndhahnebach/FreeCAD/-/pipelines?scope=branches