[#1637] Check for null parameters

codec-http/src/main/java/io/netty/handler/codec/http/DefaultHttpMessage.java

@@ -66,6 +66,9 @@ public abstract class DefaultHttpMessage extends DefaultHttpObject implements Ht
 
     @Override
     public HttpMessage setProtocolVersion(HttpVersion version) {
+        if (version == null) {
+            throw new NullPointerException("version");
+        }
         this.version = version;
         return this;
     }

codec-http/src/main/java/io/netty/handler/codec/http/DefaultHttpRequest.java

@@ -56,12 +56,18 @@ public class DefaultHttpRequest extends DefaultHttpMessage implements HttpReques
 
     @Override
     public HttpRequest setMethod(HttpMethod method) {
+        if (method == null) {
+            throw new NullPointerException("method");
+        }
         this.method = method;
         return this;
     }
 
     @Override
     public HttpRequest setUri(String uri) {
+        if (uri == null) {
+            throw new NullPointerException("method");
+        }
         this.uri = uri;
         return this;
     }

codec-http/src/main/java/io/netty/handler/codec/http/DefaultHttpResponse.java

@@ -45,6 +45,9 @@ public class DefaultHttpResponse extends DefaultHttpMessage implements HttpRespo
 
     @Override
     public HttpResponse setStatus(HttpResponseStatus status) {
+        if (status == null) {
+            throw new NullPointerException("status");
+        }
         this.status = status;
         return this;
     }