NullPointerException when FormContentFilter handles a request with no content type

[wilkinsona]

Affects: 5.2.0 snapshots

A test is failing in Boot's build. I believe it is failing because FormContentFilter is filtering a request with no content type. In deciding if it should parse the request, it calls MediaType.parseMediaType(null) (null is the request's content type) which ultimately results in a NullPointerException:

22:14:41 java.lang.NullPointerException
22:14:41	java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:936)
22:14:41	org.springframework.util.MimeTypeUtils$ConcurrentLruCache.get(MimeTypeUtils.java:437)
22:14:41	org.springframework.util.MimeTypeUtils.parseMimeType(MimeTypeUtils.java:192)
22:14:41	org.springframework.http.MediaType.parseMediaType(MediaType.java:571)
22:14:41	org.springframework.web.filter.FormContentFilter.shouldParse(FormContentFilter.java:116)
22:14:41	org.springframework.web.filter.FormContentFilter.parseIfNecessary(FormContentFilter.java:98)
22:14:41	org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:87)
22:14:41	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109)
22:14:41	org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93)
22:14:41	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109)

I suspect that 5a308ad is the cause.