Backport of gh-25088
Comment From: jhoeller
Since we don't generally assert against null in Collection arguments in 5.1.x, not even in RestTemplate, not even having a convenience method for it in Assert, I opted for making it consistent with that line through simply adding assertions to the addInterceptor methods.
Comment From: spring-projects-issues
Fixed via 4ec02a7e53175159560f97d3a9d376843a399949