Ignore empty kwrest in Data subtypes' constructors

When passing empty kwrest into a method, `hasKeyword` will be true
but there will not actually be any keyword hash in the argument
list. We need to also check for "empty" keywords before proceeding
to use any incoming kwargs hash.

Fixes jruby#9214

Author: headius

core/src/main/java/org/jruby/RubyData.java

@@ -40,6 +40,7 @@
 import static org.jruby.runtime.Arity.checkArgumentCount;
 import static org.jruby.runtime.Helpers.invokedynamic;
 import static org.jruby.runtime.ThreadContext.CALL_KEYWORD;
+import static org.jruby.runtime.ThreadContext.CALL_KEYWORD_EMPTY;
 import static org.jruby.runtime.ThreadContext.clearCallInfo;
 import static org.jruby.runtime.ThreadContext.hasKeywords;
 import static org.jruby.runtime.ThreadContext.resetCallInfo;
@@ -309,7 +310,7 @@ public static IRubyObject rbNew(ThreadContext context, IRubyObject self, IRubyOb
 
             RubyHash init;
             int callInfo = resetCallInfo(context);
-            if (hasKeywords(callInfo)) {
+            if (hasKeywords(callInfo) && (callInfo & CALL_KEYWORD_EMPTY) == 0) {
                 if (!(hashOrElt instanceof RubyHash)) {
                     throw argumentError(context, 1, 0, 0);
                 }