Minor bug in masking tool behaviour

[RalfH]

I just noticed that there is a minor bug in the behaviour of the masking tools in verison 0.9.0: When using the selecting tools rectangle and magic wand, they remain active after adding/subtracting the selection to/from the mask or when opening another image. When using the intelligent scissors tool, however, the tool becomes inactive and has to be activated again every time after applying to selection to the mask or opening a new image. It would be good if that tool would behave like the others (i.e., remain active).

[wmd]

I agree on this, it would be easier and more efficient for masking

[RalfH]

The problem is still present in version 0.9.1, and I think it should not be difficult to fix this.