Fix the security filtering to handle None as a severity.
Fix the security filtering to handle None as a severity.

GoogleCloudPlatform/runtimes-common,huyhg/runtimes-common,duggelz/runtimes-common,huyhg/runtimes-common,priyawadhwa/runtimes-common,priyawadhwa/runtimes-common,duggelz/runtimes-common,nkubala/runtimes-common,sharifelgamal/runtimes-common,cftorres/runtimes-common,sharifelgamal/runtimes-common,nkubala/runtimes-common,priyawadhwa/runtimes-common,abbytiz/runtimes-common,abbytiz/runtimes-common,nkubala/runtimes-common,sharifelgamal/runtimes-common,sharifelgamal/runtimes-common,sharifelgamal/runtimes-common,priyawadhwa/runtimes-common,priyawadhwa/runtimes-common,cftorres/runtimes-common,dlorenc/runtimes-common,nkubala/runtimes-common,priyawadhwa/runtimes-common,duggelz/runtimes-common,sharifelgamal/runtimes-common,nkubala/runtimes-common,GoogleCloudPlatform/runtimes-common,abbytiz/runtimes-common,GoogleCloudPlatform/runtimes-common,dlorenc/runtimes-common,cftorres/runtimes-common,sharifelgamal/runtimes-common,huyhg/runtimes-common,priyawadhwa/runtimes-common,dlorenc/runtimes-common