internal/lsp: stop returning errors when we can't find a snapshot
internal/lsp: stop returning errors when we can't find a snapshot

Change-Id: I319021a3339971809b6096b3271aa6b0d94ae336
Reviewed-on: https://go-review.googlesource.com/c/tools/+/216139
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools