promptForUniquename() for GFF as well as database entries

uk/ac/sanger/artemis/components/genebuilder/GeneUtils.java

@@ -837,7 +837,9 @@ public class GeneUtils
     String id = null;
     
     if(default_entry.getEMBLEntry() instanceof 
-        uk.ac.sanger.artemis.io.DatabaseDocumentEntry)
+        uk.ac.sanger.artemis.io.DatabaseDocumentEntry ||
+       default_entry.getEMBLEntry() instanceof 
+        uk.ac.sanger.artemis.io.GFFDocumentEntry)
     {  
       while(id == null ||
             id.equals("") ||