Fix a logging bug in parameter_block.h
Fix a logging bug in parameter_block.h

Not entirely sure how and why this was compiling up till now.

Thanks to Carlos Hernandez for reporting this.

Change-Id: Ieadbb8cb0a3769afe9dcef927ff0287342e44f1f

entylop/ceres-solver,stonier/ceres_solver,DougFirErickson/ceres-solver,timfel/ceres-bin,jmwalls/ceres-solver-fork,entylop/ceres-solver,stonier/ceres_solver,stonier/ceres_solver,whuaegeanse/ceres-solver,ikoruk/ceres-solver,jmwalls/ceres-solver-fork,ikoruk/ceres-solver,entylop/ceres-solver,ysonggit/ceres-solver,jmwalls/ceres-solver-fork,whuaegeanse/ceres-solver,ikoruk/ceres-solver,kartikkumar/ceres-solver,whuaegeanse/ceres-solver,kartikkumar/ceres-solver,jmwalls/ceres-solver-fork,timfel/ceres-bin,DougFirErickson/ceres-solver,DougFirErickson/ceres-solver,ysonggit/ceres-solver,DougFirErickson/ceres-solver,ysonggit/ceres-solver,timfel/ceres-bin,whuaegeanse/ceres-solver,kartikkumar/ceres-solver,ikoruk/ceres-solver,stonier/ceres_solver,ikoruk/ceres-solver,timfel/ceres-bin,ysonggit/ceres-solver,entylop/ceres-solver,kartikkumar/ceres-solver