Fix known_only panic by short circuiting for NULL before checking has… #2947

	---
	name: Semgrep Differential Scan
	on: pull_request

	jobs:
	semgrep-diff:
	runs-on: ubuntu-latest
	container:
	image: returntocorp/semgrep

	steps:
	# step 1
	- name: clone application source code
	uses: actions/checkout@v3
	with:
	fetch-depth: 0

	# step 2
	- name: differential scan
	run: \|
	semgrep scan \
	--error \
	--metrics=off \
	--baseline-commit ${{ github.event.pull_request.base.sha }} \
	--config="p/default"

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