refactor: minor code changes in karma `AngularAssetsMiddleware` #934

Job	Run time
list	22s
workflow (devkit-core-tests)	1m 2s
workflow (devkit-core-tests-rerun)	1m 5s
workflow (modules-builder-tests)	1m 32s
workflow (build-unit-tests)	2m 1s
workflow (build-cli)	1m 20s
	7m 22s

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