Fsdk/Misc: fix NRE if legacy #1582

Job	Run time
linux-oldLTS-github--dotnet-and-msbuild	8m 49s
linux-oldLTS-github--dotnet-and-xbuild	9m 7s
macOS--dotnet6-and-mono	11m 10s
macOS--mono	8m 38s
linux-newLTS-github--dotnet-and-msbuild	7m 46s
linux-newLTS-github--dotnet-and-xbuild	9m 0s
linux-oldLTS-vanilla--newmono	6m 46s
linux-oldLTS-vanilla--stockmono	5m 51s
linux-newLTS-vanilla--dotnet6	7m 43s
linux-newLTS-vanilla--newmono	6m 18s
linux-newLTS-vanilla--stockmono	5m 9s
windows--dotnet6	9m 31s
windows--legacyFramework	16m 6s
sanity-check	56s
publish	50s
	1h 53m 40s

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