Error: Could not find file in 'getValidSourceFile' during 'getApplicableRefactors'

[aozgaa]

This issue comes from crash dumps in telemetry. We've tried to de-duplicate issues on a best-effort basis, comparing the sequence of methods called and the command requested while ignoring line numbers.
TypeScript Version Prefix: 2.7.2
VSCode Version 1.20.1
command requested: getApplicableRefactors
hitting sessions: 142
proportion of all sessions: 0.010121168923734854
five line hash: a33b9c67084ab38af033d15bccfe5ed7
stack

Error: Could not find file
    at getValidSourceFile (tsserver.js:82897:23)
    at Object.getApplicableRefactors (tsserver.js:83496:24)
    at IOSession.Session.getApplicableRefactors (tsserver.js:90354:53)
    at Session.handlers.ts.createMapFromTemplate._a.(anonymous function) (tsserver.js:89310:61)
    at unknown (tsserver.js:90553:88)
    at IOSession.Session.executeWithRequestId (tsserver.js:90544:28)
    at IOSession.Session.executeCommand (tsserver.js:90553:33)
    at IOSession.Session.onMessage (tsserver.js:90573:35)
    at Interface.<anonymous> (tsserver.js:91774:27)
    at emitOne (events.js:96:13)
    at Interface.emit (events.js:191:7)
    at Interface._onLine (readline.js:241:10)
    at Interface._normalWrite (readline.js:384:12)
    at Socket.ondata (readline.js:101:10)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at readableAddChunk (_stream_readable.js:178:18)
    at Socket.Readable.push (_stream_readable.js:136:10)
    at Pipe.onread (net.js:560:20)

[ghost]

Duplicate of #20785
@aozgaa This one has a lot of duplicates, could we deduplicate better?