natClass.cc (getSignature): Don't try to dereference param_types if it is null.

natClass.cc (getSignature): Don't try to dereference param_types if it is null.

	* java/lang/natClass.cc (getSignature): Don't try to dereference
	param_types if it is null. Instead, take this to mean "no parameters".
	* java/lang/TreeMap.java (TreeIterator.next): Throw
	NoSuchElementException in preference to
	ConcurrentModificationException.
	(TreeIterator.remove): Throw IllegalStateException in preference to
	ConcurrentModificationException.
	(SubMap.firstKey): Do a better check for empty SubMap, and if it is,
	throw a NoSuchElementException.
	(SubMap.lastKey): Likewise.

From-SVN: r39658