internal/lsp: fix nil pointer in hover when (types.Object).Pkg() is nil

We haven't been able to reproduce this scenario, but it may be possible
when the user is in a broken state. Avoid panicking by gating every
use of obj.Pkg() with nil checks.

Fixes golang/go#44300

Change-Id: Ia0c56a7fd5d6b89795dded1efdf05838f3de8209
Reviewed-on: https://go-review.googlesource.com/c/tools/+/292671
Trust: Rebecca Stambler <[email protected]>
Run-TryBot: Rebecca Stambler <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>

Author: stamblerre

internal/lsp/source/hover.go

@@ -187,6 +187,10 @@ func HoverIdentifier(ctx context.Context, i *IdentifierInfo) (*HoverInformation,
 			}
 		}
 	}
+	if obj.Pkg() == nil {
+		event.Log(ctx, fmt.Sprintf("nil package for %s", obj))
+		return h, nil
+	}
 	h.importPath = obj.Pkg().Path()
 	h.LinkPath = h.importPath
 	if mod, version, ok := moduleAtVersion(h.LinkPath, i); ok {