lookup the dbkey and not the value of a data_table

The option "Perform Bias Correction" is not working for us. I found the following thread that is describing our issue:
http://gmod.827538.n3.nabble.com/Solution-for-Error-running-cuffdiff-Error-cannot-open-reference-GTF-file-CONDITION-CONTROL-for-readig-td3733770.html

But is seems to be not fixed. I was able to track it down to the following line:
https://github.com/galaxyproject/tools-devteam/blob/master/tool_collections/cufflinks/cuffdiff/cuffdiff_wrapper.xml#L41

`value` needs to be replaced by `dbkey` or?