module-jni: crash in handling Java calls to a varargs method from another language with no args passed

[davidnich]

ex:

Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
C  [libqore.so.12.0.3+0x1251c4]  QoreListNode::size() const+0x4
C  [jni-api-1.3.qmod+0x12113d]  jni::BaseMethod::convertArgsToArray(QoreListNode const*, unsigned long, unsigned long, jni::JniExternalProgramData*) const+0x537
C  [jni-api-1.3.qmod+0x121c58]  jni::BaseMethod::invoke(_jobject*, QoreListNode const*, QoreProgram*, int) const+0x4dc
C  [jni-api-1.3.qmod+0x129e77]  jni::QoreJniFunctionalInterface::execValue(QoreListNode const*, ExceptionSink*) const+0x243

Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
j  org.qore.jni.JavaClassBuilder.doNormalCall0(Ljava/lang/String;JJJ[Ljava/lang/Object;)Ljava/lang/Object;+0
j  org.qore.jni.JavaClassBuilder.doNormalCall(Ljava/lang/String;JJJ[Ljava/lang/Object;)Ljava/lang/Object;+7
j  qoremod.QUnit.Test.main()J+13
j  DynamicBasicsSimpleWfTest.<init>([Ljava/lang/String;)V+24
j  DynamicBasicsSimpleWfTest.main([Ljava/lang/String;)V+5
v  ~StubRoutines::call_stub