Neil Williams' patch to fix the book-merge test.

[Derek Atkins]

Log Message:
-----------
Neil Williams' patch to fix the book-merge test.

	* src/engine/test/test-book-merge.c: targetEnt is always NULL
	  during MERGE_NEW so don't test it in that case.

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/engine/test:
        test-book-merge.c