tracker-extract: Do not add statistics data if no module handled the file
tracker-extract: Do not add statistics data if no module handled the file

This prevents a crash when reporting the statistics later, as there is a
NULL key that is expected to be a GModule.

outofbits/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,hoheinzollern/tracker,hoheinzollern/tracker,hoheinzollern/tracker,hoheinzollern/tracker