fix(@schematics/angular): use null objects and callbacks in karma-to-… #10503

Job	Run time
lint	2m 2s
build-e2e-windows	4m 28s
build	15m 2s
e2e-windows (24, webpack, 4)	13m 16s
e2e-windows (24, webpack, 0)	19m 24s
e2e-windows (24, webpack, 3)	13m 37s
e2e-windows (24, esbuild, 1)	12m 19s
e2e-windows (24, esbuild, 0)	12m 44s
e2e-windows (24, esbuild, 4)	13m 50s
e2e-windows (24, webpack, 5)	13m 6s
e2e-windows (24, esbuild, 5)	13m 0s
e2e-windows (24, esbuild, 2)	11m 30s
e2e-windows (24, webpack, 1)	24m 9s
e2e-windows (24, esbuild, 3)	16m 16s
e2e-windows (24, webpack, 2)	16m 54s
Browser Compatibility Tests	0s
test	0s
e2e-package-managers	0s
publish-snapshots	0s
e2e-snapshots	0s
e2e	0s
	3h 21m 37s

Provide feedback