staticroutebfd fails to handle static route del notification

[vivekrnv]

Description

staticroutebfd throwing exception and restarting bgp container while handling a static route delete.

Steps to reproduce the issue:

1. config interface ip add Ethernet64 3.3.3.3/24
2. config route add prefix 50.50.50.0/24 nexthop 3.3.3.4
3. config route del prefix 50.50.50.0/24 nexthop 3.3.3.4

Describe the results you received:

May 30 22:54:08.017236 r-panther-simx-13 DEBUG bgp#staticroutebfd: Received message : '('default|50.50.50.0/24', 'DEL', ())'
May 30 22:54:08.017236 r-panther-simx-13 DEBUG bgp#bgpcfgd: Received message : '('default|50.50.50.0/24', 'DEL', ())'
May 30 22:54:08.020484 r-panther-simx-13 DEBUG bgp#bgpcfgd: CONFIG_DB Static route default|50.50.50.0/24 is scheduled for updates. ['no ip route 50.50.50.0/24 3.3.3.4 tag 1']
May 30 22:54:08.020484 r-panther-simx-13 CRIT bgp#staticroutebfd: Got an exception 'NoneType' object is not subscriptable: Traceback: Traceback (most recent call last):#012  File "/usr/local/lib/python3.9/dist-packages/staticroutebfd/main.py", line 745, in main#012    do_work()#012  File "/usr/local/lib/python3.9/dist-packages/staticroutebfd/main.py", line 737, in do_work#012    sr_bfd.run()#012  File "/usr/local/lib/python3.9/dist-packages/staticroutebfd/main.py", line 733, in run#012    callback(key, op, dict(fvs))#012  File "/usr/local/lib/python3.9/dist-packages/staticroutebfd/main.py", line 536, in static_route_callback#012    self.static_route_del_handler(key, True)#012  File "/usr/local/lib/python3.9/dist-packages/staticroutebfd/main.py", line 507, in static_route_del_handler#012    nh_vrf = nh_vrf_list[index]#012TypeError: 'NoneType' object is not subscriptable
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd Traceback (most recent call last):
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd   File "/usr/local/bin/staticroutebfd", line 8, in <module>
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd     sys.exit(main())
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd   File "/usr/local/lib/python3.9/dist-packages/staticroutebfd/main.py", line 745, in main
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd     do_work()
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd   File "/usr/local/lib/python3.9/dist-packages/staticroutebfd/main.py", line 737, in do_work
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd     sr_bfd.run()
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd   File "/usr/local/lib/python3.9/dist-packages/staticroutebfd/main.py", line 733, in run
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd     callback(key, op, dict(fvs))
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd   File "/usr/local/lib/python3.9/dist-packages/staticroutebfd/main.py", line 536, in static_route_callback
May 30 22:54:08.020484 r-panther-simx-13 DEBUG bgp#bgpcfgd: execute command '['vtysh', '-f', '/tmp/tmpkldpilww']'.
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd     self.static_route_del_handler(key, True)
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd   File "/usr/local/lib/python3.9/dist-packages/staticroutebfd/main.py", line 507, in static_route_del_handler
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd     nh_vrf = nh_vrf_list[index]
May 30 22:54:08.020484 r-panther-simx-13 INFO bgp#supervisord: staticroutebfd TypeError: 'NoneType' object is not subscriptable

And also restarts the bgp container

Describe the results you expected:

staticroutebfd should handle the del notification gracefully

Output of show version:

master labels built with this #13789

Additional information you deem important (e.g. issue happens only occasionally):

[prsunny]

Looking into this!

[prsunny]

Fix PR - #15269