Rigidity slider can become disabled while there is still MP (multicellular?)

[hhyyrylainen]

report came in that in multicellular the rigidity slider got disabled while there were 8 MP remaining. This might be multicellular specific unless my refactoring caused the microbe editor to also break like this.

Probably can be fixed by going through the actions in the editor and make sure it probably updates the rigidity state. Also when switching to the cell editor tab needs to make sure that the logic there will set things correctly for that tab.