Only display image info if that exists

When a new search is performed in the MWMediaSearchWidget,
image thumbnail details are extracted from the API's imageinfo.
In some cases, this parameter does not exist. MWMediaResultWidget
relies on that parameter to get image details like 'src' and
width/height. Without it the search fails.

This fix makes sure that the thumbnail result is only displayed
if there are 'imageinfo' details at all. Otherwise, the image
result is ignored.

Bug: 61392
Change-Id: I5261059bb42d3a57441514eafaa0bffa3a3c3ba4
Merge "Only display image info if that exists"