Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
check for valid simpleXML object before foreach()

Few METS files doesn't provide the proper XML namespace for df:links. In i
this case no simpleXML object is returned by xpath(). The following foreach()
throws a PHP warning.
Merge pull request #4 from albig/master

check for valid simpleXML object before foreach()