The goimports code tries to read source from disk if none is supplied,
but the completion functions don't need source. Pass a dummy slice.
Fixesgolang/go#36671.
Change-Id: Ieecc9ee75d39f8f165c7b9764ff49c8334a7fcd2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/215681
Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>