Can't move blocks in data flow graph mode

[Achllle]

When in the state machine editor, blocks' location freezes after one move after enabling the data flow graph mode.

steps to reproduce

1. launch the flexbe app
2. open any behavior, e.g. example behavior
3. in the state machine editor, select 'data flow graph'
4. move a state and drop it. Try moving it around again, this will fail.

Once blocks lock into place, you can only move any block again by relaunching FlexBE.

[pschillinger]

Need to check, but I would assume this has been introduced recently by this commit.