When the MWMediaResultWidget receives a file that has no graphical
represenation (width:0 height:0) it uses minWidth of 30px for width of the
thumbnail.
This is, for example, the case with PDF files if the PdfHandler extension is
not active.
This patch solves the issue by falling back to the thumbwidth/thumbheight
values if width/height are 0.
Change-Id: I6bdaf1aafc0c45e26d31cd9dd9504e193f04e717