Fixes null pointer dereference in print_http_hdr
Fixes null pointer dereference in print_http_hdr

issue found by clang-analyzer

vmamidi/trafficserver,bryancall/trafficserver,chitianhao/trafficserver,pbchou/trafficserver,pbchou/trafficserver,vmamidi/trafficserver,duke8253/trafficserver,davidbz/trafficserver,SolidWallOfCode/trafficserver,dyrock/trafficserver,SolidWallOfCode/trafficserver,davidbz/trafficserver,duke8253/trafficserver,duke8253/trafficserver,SolidWallOfCode/trafficserver,chitianhao/trafficserver,pbchou/trafficserver,chitianhao/trafficserver,duke8253/trafficserver,bryancall/trafficserver,davidbz/trafficserver,pbchou/trafficserver,bryancall/trafficserver,pbchou/trafficserver,duke8253/trafficserver,dyrock/trafficserver,davidbz/trafficserver,davidbz/trafficserver,dyrock/trafficserver,SolidWallOfCode/trafficserver,chitianhao/trafficserver,chitianhao/trafficserver,bryancall/trafficserver,dyrock/trafficserver,vmamidi/trafficserver,bryancall/trafficserver,vmamidi/trafficserver,davidbz/trafficserver,chitianhao/trafficserver,pbchou/trafficserver,vmamidi/trafficserver,duke8253/trafficserver,dyrock/trafficserver,chitianhao/trafficserver,SolidWallOfCode/trafficserver,SolidWallOfCode/trafficserver,SolidWallOfCode/trafficserver,dyrock/trafficserver,duke8253/trafficserver,bryancall/trafficserver,dyrock/trafficserver,vmamidi/trafficserver