Spring Security RequestAttributeSecurityContextRepository.loadContext(HttpServletRequest) should never return null SecurityContext

Describe the bug Based on this comment, if the request attribute is null, an error is thrown from the strategy:

java.lang.IllegalArgumentException: A Supplier<SecurityContext> returned null and is not allowed.
    at org.springframework.util.Assert.notNull(Assert.java:201) ~[spring-core-6.0.0-M5.jar:6.0.0-M5]
    at org.springframework.security.core.context.ThreadLocalSecurityContextHolderStrategy.lambda$setDeferredContext$2(ThreadLocalSecurityContextHolderStrategy.java:68) ~[spring-security-core-6.0.0-SNAPSHOT.jar:6.0.0-SNAPSHOT]
    at org.springframework.security.core.context.ThreadLocalSecurityContextHolderStrategy.getContext(ThreadLocalSecurityContextHolderStrategy.java:43) ~[spring-security-core-6.0.0-SNAPSHOT.jar:6.0.0-SNAPSHOT]

Expected behavior RequestAttributeSecurityContextRepository#loadContext(HttpServletRequest) should return an empty context if the request attribute is null.

Comment From: github-actions[bot]

Fixed via 269c711a6409c8f4125f261dd047321f94b58255