multiarray: fix a problem in the test where an end() iterator would be dereferenced.
multiarray: fix a problem in the test where an end() iterator would be dereferenced.

dstoe/vigra,dagophil/vigra,dagophil/vigra,dagophil/vigra,dstoe/vigra,funkey/vigra,dstoe/vigra,dagophil/vigra,funkey/vigra,dstoe/vigra,dstoe/vigra,dstoe/vigra,funkey/vigra,dstoe/vigra,funkey/vigra,funkey/vigra,dagophil/vigra,dagophil/vigra,dagophil/vigra,funkey/vigra,funkey/vigra