Gas pipeline calculations fail at low flow rates

**Describe the bug**
It seems to be a numerical challenge with the one phase gas pipeline solver, that makes calculations at low flow rate to crash.

**To Reproduce**
Set a low gas flow rate (eg. 1 MSm3/day in test:
PipelineTest

Start with the PipelineTest mentioned in the report and reproduce the one-phase gas pipeline calculation at a flow rate of 1 MSm3/day. Trace the low-flow solver failure and inspect its numerical handling; done means the calculation no longer crashes and the regression is covered by the relevant test.

Written by the indexing model from the issue text.