"panic: interface conversion: interface is nil, not fs.FileInfo" in internal/execute/tsctests tests

[jakebailey]

https://github.com/microsoft/typescript-go/actions/runs/19048910796/job/54403963356

panic: interface conversion: interface is nil, not fs.FileInfo

goroutine 19498 [running]:
github.com/microsoft/typescript-go/internal/collections.(*SyncMap[...]).Load(0x223cb60, {0xc0035fa100, 0x3b})
	/mnt/vss/_work/typescript-go/typescript-go/internal/collections/syncmap.go:19 +0xdf
github.com/microsoft/typescript-go/internal/vfs/cachedvfs.(*FS).Stat(0xc004a40360, {0xc0035fa100, 0x3b})
	/mnt/vss/_work/typescript-go/typescript-go/internal/vfs/cachedvfs/cachedvfs.go:126 +0x71
github.com/microsoft/typescript-go/internal/execute/incremental.GetMTime({0x2224da8, 0xc001d1edc0}, {0xc0035fa100, 0x3b})
	/mnt/vss/_work/typescript-go/typescript-go/internal/execute/incremental/host.go:33 +0x58
github.com/microsoft/typescript-go/internal/execute/build.(*host).loadOrStoreMTime(0xc00250a8c0, {0xc0035fa100, 0x3b}, 0x0, 0x1)
	/mnt/vss/_work/typescript-go/typescript-go/internal/execute/build/host.go:95 +0x1ea
github.com/microsoft/typescript-go/internal/execute/build.(*host).GetMTime(...)
	/mnt/vss/_work/typescript-go/typescript-go/internal/execute/build/host.go:77
github.com/microsoft/typescript-go/internal/execute/build.(*BuildTask).hasUpdate(0xc003763a00, 0xc003dbb170, {0xc0010b6300, 0x3b})
	/mnt/vss/_work/typescript-go/typescript-go/internal/execute/build/buildtask.go:756 +0x745
github.com/microsoft/typescript-go/internal/execute/build.(*Orchestrator).DoCycle.func1.1()
	/mnt/vss/_work/typescript-go/typescript-go/internal/execute/build/orchestrator.go:267 +0x6b
github.com/microsoft/typescript-go/internal/core.(*parallelWorkGroup).Queue.func1()
	/mnt/vss/_work/typescript-go/typescript-go/internal/core/workgroup.go:40 +0x2f
sync.(*WaitGroup).Go.func1()
	/mnt/vss/_work/_tool/go/1.25.3/x64/src/sync/waitgroup.go:239 +0x5e
created by sync.(*WaitGroup).Go in goroutine 19635
	/mnt/vss/_work/_tool/go/1.25.3/x64/src/sync/waitgroup.go:237 +0x87
FAIL	github.com/microsoft/typescript-go/internal/execute/tsctests	1.169s

This should be reproducible given it came from CI.