Followup 0165a53: don't store an mw.Title object instead of a string in TemplateModel
0165a53 overlooked the fact that 'name' is also passed to
the MWTemplateModel constructor, and there it really does
always need to be a string, not magically either a string
or an mw.Title object. Oops :(
Bug: 72961
Change-Id: I0b20f0768aae4d9cc9f7af268abd0a704b6adc3a