Fix change summary in SpecialSetSiteLink if no badges are set

ChangeOpSiteLink expects to get null if we don't want to set
badges, not an empty array.

Bug: 62546
Change-Id: I157ae05b4bf20a296d4270df21898ed31c22a967
(cherry picked from commit 2630c7c6c5b42c78891d3d35e2dd2168601464e7)