Fsdk/Misc: fix NRE if legacy #1578

Job	Run time
linux-oldLTS-github--dotnet-and-xbuild	7m 46s
linux-oldLTS-github--dotnet-and-msbuild	8m 30s
macOS--mono	7m 21s
macOS--dotnet6-and-mono	9m 35s
linux-newLTS-github--dotnet-and-msbuild	7m 31s
linux-newLTS-github--dotnet-and-xbuild	8m 6s
linux-oldLTS-vanilla--stockmono	5m 53s
linux-oldLTS-vanilla--newmono	7m 9s
linux-newLTS-vanilla--dotnet6	7m 39s
linux-newLTS-vanilla--newmono	6m 27s
windows--legacyFramework	17m 43s
linux-newLTS-vanilla--stockmono	6m 21s
windows--dotnet6	10m 47s
sanity-check	1m 20s
publish	51s
	1h 52m 59s

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