vtysh: fix rare crash(es)

[qlyoung]

Couple code paths end up trying to dereference vty->of which can be null
in one special case.

Signed-off-by: Quentin Young qlyoung@cumulusnetworks.com

[mjstapp]

Would it make sense to add the check to vty_out itself - to avoid using ->of if it's NULL?

[qlyoung]

I thought about that, but it really probably should crash anywhere else but here, and vtysh is already a cesspit of bs so I don't feel too torn up about these checks

[LabN-CI]

🚧 Basic BGPD CI results: Partial FAILURE, 2 tests failed

Results table

_	_
Result	SUCCESS git merge/4879 52038ac
Date	08/23/2019
Start	16:30:20
Finish	16:52:08
Run-Time	21:48
Total	1815
Pass	1813
Fail	2
Valgrind-Errors	0
Valgrind-Loss	0
Details	vncregress-2019-08-23-16:30:20.txt
Log	autoscript-2019-08-23-16:31:13.log.bz2
Memory	430 428 360

For details, please contact louberger

[NetDEF-CI]

Continuous Integration Result: SUCCESSFUL

Congratulations, this patch passed basic tests

Tested-by: NetDEF / OpenSourceRouting.org CI System

CI System Testrun URL: https://ci1.netdef.org/browse/FRR-FRRPULLREQ-8689/

This is a comment from an automated CI system.
For questions and feedback in regards to this CI system, please feel free to email
Martin Winter - mwinter (at) opensourcerouting.org.

---

CLANG Static Analyzer Summary

• Github Pull Request 4879, comparing to Git base SHA 401ba2a

No Changes in Static Analysis warnings compared to base

1 Static Analyzer issues remaining.

See details at
https://ci1.netdef.org/browse/FRR-FRRPULLREQ-8689/artifact/shared/static_analysis/index.html

[mjstapp]

looks good