Change use of maybe-defined "mkws_jQuery" to avoid assigning to an undefined variable.

Change use of maybe-defined "mkws_jQuery" to avoid assigning to an undefined variable.
Fixes the "make phantomjs" Jenkins error:
	Strict mode forbids implicit creation of global property 'mkws_jQuery'

Note: not yet tested as part of installation (which we need so we can
check that Seb's widgets embedded in the blog still work). I am
pushing so that I can onto the live site and verify that. If there's a
problem there, I'll revert and try again.