Fix undefined variable: $parserOutput in ApiMobileView::getData

ApiMobileView::getData never assigns a value to $parserOutput when the page is
a file page, and thus if ( $parserOutput ) { .. } check triggers an undefined
variable warning.

Change-Id: Iae788b186ee18b44a5153eb59571524890fc05fd
(cherry picked from commit 0310cd07ea86ca15c26a825e1fc2076e85edc407)