Avoid logging a NullPointerException if IlluminaBasecallsToFastq is
started with FORCE_GC=false.

GC timer write to the 'log' instead of directly to System.out. There is
really no reason to handle this information differently than other
logging.
Merge pull request #14 from nnordborg/gc-timer-npe

FORCE_GC=false causes NPE in log