Fix macOS crash in NetworkChange when the run loop thread already exited - #131867

Fix macOS crash in NetworkChange when the run loop thread already exited#131867

wfurt merged 2 commits into

dotnet:maindotnet/runtime:mainfrom

isaacisland:fix-osx-networkchange-null-runloopisaacisland/runtime:fix-osx-networkchange-null-runloopCopy head branch name to clipboard