internal/lsp/source: fix bug introduced by CL 246757
internal/lsp/source: fix bug introduced by CL 246757

CL 246757 resulted in an infinite loop because the value of "o" is
never updated.

Change-Id: I79cf265349838de19089c4468128c565a9a3cda3
Reviewed-on: https://go-review.googlesource.com/c/tools/+/247182
Run-TryBot: Rebecca Stambler <d7cf11e5f299d88ea8348366a9fc4f7c335c3afa@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Josh Baum <51d083aa9f556b003ee94647c095167dec281ba9@google.com>

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