Make Quick Pol Image quicklook crashes on bad data

[semaphoreP]

On some bad data (poor conditions and star centering), the make pol QL image crashes on histogram making. It appears there are no good pixel values for the histogram. We should add some error handling to make this fail more gracefully (empty plot?)

The following error obtained on running on HD 110058 on 2016-01-26.

% Execution halted at: GPI_MAKE_POL_QL_IMAGE  102
   /home/sda/jwang/GPI/pipeline/pipeline/primitives/gpi_make_pol_ql_image.pro
%                      GPIPIPELINEBACKBONE::RUNMODULE  910
   /home/sda/jwang/GPI/pipeline/pipeline/backbone/gpipipelinebackbone__define
  .pro
%                      GPIPIPELINEBACKBONE::REDUCE  730
   /home/sda/jwang/GPI/pipeline/pipeline/backbone/gpipipelinebackbone__define
  .pro
%                      GPIPIPELINEBACKBONE::RUN_ONE_RECIPE  622
   /home/sda/jwang/GPI/pipeline/pipeline/backbone/gpipipelinebackbone__define
  .pro
%                      GPIPIPELINEBACKBONE::RUN_QUEUE  453
   /home/sda/jwang/GPI/pipeline/pipeline/backbone/gpipipelinebackbone__define
  .pro
%                      GPI_LAUNCH_PIPELINE   99
   /home/sda/jwang/GPI/pipeline/pipeline/backbone/gpi_launch_pipeline.pro
%                      $MAIN$          
% Program caused arithmetic error: Floating divide by 0
% Program caused arithmetic error: Floating illegal operand
IDL> w_good
          -1