Relax Http Header Validation to just "not null"

The code
http://anonsvn.jboss.org/repos/labs/labs/jbossesb/tags/JBESB_4_7_CP2_ER4/product/rosetta/src/org/jboss/soa/esb/http/HttpHeader.java

checks
AssertArgument.isNotNullAndNotEmpty(name, "name");
AssertArgument.isNotNullAndNotEmpty(value, "value");

However, there can be occasions where the value is empty. The condition should be relaxed to "not null" (not sure if it could ever be null)