Streetcar track removal fails when bank balance negative

[bfut]

Version of OpenTTD

20200407-master-gd50e4641ae

Expected result

Removing streetcar track generates income, e.g. €156.

Actual result

Removing streetcar track issues error, e.g. "Not enough cash - requires -€156", when bank balance is negative, but generates income when bank balance is positive. Haven't checked bank balance equal to zero.

Steps to reproduce

1. Start new game, making sure to load a tram NewGRF. Tested with Fake Subways + other NewGRFs, and vanilla + CZTR Tram set)
2. Build streetcar tracks.
3. Reduce bank balance until negative.
4. Attempt removing streetcar track, see screenshot.
   

Note: may be related to #7656, even though not a duplicate

[James103]

Can reproduce in 1.10.0 stable, tried removing tram track on both normal road and bridges. Only occurs if current bank balance (negative) plus removal cost (positive) < 0.

[TrueBrain]

Thank you @James103 for that final remark ("Only occurs if current bank balance (negative) plus removal cost (positive) < 0."). Took me a while to reproduce :D I was balancing in the in-between at first, not being able to reproduce :D Bug confirmed, fix incoming :)