[link]: in some cases missing

[tanteuschi]

Expected behavior The [link]: element should display link address of paper.

Actual behavior [link]: address in some cases missing even though the Link Button on the right is leading to link address.

How to reproduce

Open the map „heart disease“ in Pubmed: https://openknowledgemaps.org/map/feb3c2d3c7e9a61a5ccbe9ddf9e96ced Search for „Changes in the Leading Cause of Death..“ paper. [link]: address is missing. But the button on the right „Link plus icon“ is leading to papers link address: https://www.ncbi.nlm.nih.gov/pubmed/27598767. This means the address is known to us and should be displayed under [link]: element