[🚧] REST: Request fails if one of two parameters is not specified

[finnWellers]

Describe the bug
When expecting more than one request parameter and at least one is not provided, the request fails with a

java.lang.IllegalArgumentException: argument "content" is null
	at com.fasterxml.jackson.databind.ObjectMapper._assertNotNull(ObjectMapper.java:4413) ~[jackson-databind-2.10.2.jar:2.10.2]
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3172) ~[jackson-databind-2.10.2.jar:2.10.2]
	at de.fearnixx.jeak.service.controller.connection.HttpServer.fromJson(HttpServer.java:146) ~[classes/:?]
	at de.fearnixx.jeak.service.controller.connection.HttpServer.transformRequestOption(HttpServer.java:90) ~[classes/:?]
	at de.fearnixx.jeak.service.controller.controller.SparkAdapter.lambda$generateRoute$3(SparkAdapter.java:128) ~[classes/:?]
	at spark.RouteImpl$1.handle(RouteImpl.java:72) ~[spark-core-2.9.1.jar:?]
	at spark.http.matching.Routes.execute(Routes.java:61) ~[spark-core-2.9.1.jar:?]
	at spark.http.matching.MatcherFilter.doFilter(MatcherFilter.java:134) ~[spark-core-2.9.1.jar:?]
	at

Error