Merge branch 'hotfix/JAL-1524' into Release_2_8_2_Branch

diff --cc src/jalview/gui/PopupMenu.java
index 83544d7,e2b6536..3cf4fe0
--- 1/src/jalview/gui/PopupMenu.java
--- 2/src/jalview/gui/PopupMenu.java
+++ b/src/jalview/gui/PopupMenu.java
@@@ -519,9 -478,9 +519,9 @@@ public class PopupMenu extends JPopupMe
        {
          Vector<PDBEntry> pes = (Vector<PDBEntry>) sq.getDatasetSequence()
                  .getPDBId();
-         if (pes != null)
+         if (pes != null && pes.size()>0)
          {
 -          reppdb.put(pes.get(0).getId(),pes.get(0));
 +          reppdb.put(pes.get(0).getId(), pes.get(0));
            for (PDBEntry pe : pes)
            {
              pdbe.put(pe.getId(), pe);