internal/lsp: fix nil pointer in textDocument/didClose

Fixes golang/go#35165

Change-Id: I1a4cb2bae89c2eeb52908c622ce17913f3c2a3c5
Reviewed-on: https://go-review.googlesource.com/c/tools/+/204823
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/internal/lsp/text_synchronization.go b/internal/lsp/text_synchronization.go
index 303f66f..4019dac 100644
--- a/internal/lsp/text_synchronization.go
+++ b/internal/lsp/text_synchronization.go
@@ -155,6 +155,7 @@
 	f, err := view.GetFile(ctx, uri)
 	if err != nil {
 		log.Error(ctx, "no file", err, telemetry.URI)
+		return nil
 	}
 	_, cphs, err := view.CheckPackageHandles(ctx, f)
 	if err != nil {