Fixed bug in updateWeights.  Now returns if numItems is zero (probably occurs on first pass before activity is published).  Also fixed bug that attempted to print STDP variables when stdpFlag is zero.
Fixed bug in updateWeights.  Now returns if numItems is zero (probably occurs on first pass before activity is published).  Also fixed bug that attempted to print STDP variables when stdpFlag is zero.

git-svn-id: 602a26e73ae9f2a14e2bb95676f2e137fcc39919@1317 7c0444ca-5550-0410-9008-faecdbe78eb5

dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,PetaVision/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV