Monitor shows stacktrace when trying to populate a value

[kss-espeo]

Steps to reproduce:

Configure environment as per https://gardener.readthedocs.io/en/latest/getting-started.html
Monitor UI correctly shows: http://prntscr.com/nuzg7o
Submit a sample request: http://prntscr.com/nuzgk7
Monitor shows the request with value unpopulated: http://prntscr.com/nuzivr
Wait few seconds
Expected: Monitor shows the request with value populated
Actual: An error is being shown: http://prntscr.com/nuzht7