Reduce other projects sidebar initialization

Don't attempt to initialize the sidebar if the current page
is not linked with any item.

Change-Id: I154a67310a8d7b4beb68b1930d9bbc290eb76c66
(cherry picked from commit 888a7f476a41710456fac41d3524a1434a934a9c)
Merge "Reduce other projects sidebar initialization" into wmf/1.25wmf10