Uncontrolled vessels can enter an uncontrollable, continuously accellerating spin

[dvrabel]

Uncontrolled vessel (e.g., one with a command pod but no kerbal pilot) can enter  an uncontrollable, continuously accelerating spin if an SAS mode is selected.

Steps to reproduce:

1. Create a craft with a empty command pod and an undockable probe core.

2. Get the craft into stable orbit (the bug likely occurs in other situations but the effect is easier to see when in orbit).

3. Decouple the probe core, leaving the main vessel with no control.

4. Note that SAS appears to be enabled but cannot be disabled ("No Vessel Control").

5. Set the SAS mode to prograde (or any other setting).

6. Observe how the vessel starts to spin at an increasing rate without stopping.

Setting another SAS mode (prograde/retrograde/lock) seems to do nothing, and SAS itself cannot recover.

Probably unhelpful speculation:

I would suspect that setting an SAS mode causes the SAS module to be incorrectly enabled for a single simulation tick and the SAS module starts the reaction wheel to correct the vessel heading. On subsequent ticks the SAS module sees that it should be disabled (no control) and thus never turns off the reaction wheel, leaving the reaction wheel to spin the vessel faster and faster.