Making profile_icon_url()'s validation a little more logical

Bug 1308294: The code doesn't *really* need profileicon or email,
because it can always fall back to showing the anonymous user icon.
However, the lack of profileicon and email fields can indicating
a coding problem, so we should show a warning if they're missing.

Change-Id: I9926b7a4457049ef097e16d7999f109a623f2644
Merge "Making profile_icon_url()'s validation a little more logical"