Backend: handle null response from Eth server #3978

Job	Run time
macOS--dotnet6-and-mono	5m 26s
macOS--mono-only	7m 11s
linux22-github--dotnet-and-newmono	4m 11s
macOS--dotnet6-only	4m 39s
windows--dotnet6-and-legacyFramework	5m 22s
linux22-github--dotnet-and-mono	3m 59s
windows--dotnet6-only	5m 54s
windows--legacyFramework-only	12m 22s
linux20-github--dotnet-and-mono	3m 50s
linux20-github--dotnet-and-newmono	4m 4s
linux20-vanilla--newmono-only	6m 52s
linux20-vanilla--stockmono-only	5m 39s
linux22-vanilla--newmono-only	6m 39s
linux22-vanilla--stockdotnet6-and-newmono	6m 3s
linux22-vanilla--stockdotnet6-and-stockmono	5m 19s
linux22-vanilla--stockdotnet6-only	5m 12s
linux22-vanilla--stockmono-only	5m 42s
conventions	1m 25s
snap_pkg	4m 22s
	1h 44m 11s

Provide feedback