JAL-1691 defensive check for null

diff --git a/src/jalview/datamodel/HiddenSequences.java b/src/jalview/datamodel/HiddenSequences.java
index 35e7930..929e56e 100755 (executable)
--- a/src/jalview/datamodel/HiddenSequences.java
+++ b/src/jalview/datamodel/HiddenSequences.java
@@ -278,11 +278,14 @@ public class HiddenSequences
 
   public boolean isHidden(SequenceI seq)
   {
-    for (int i = 0; i < hiddenSequences.length; i++)
+    if (hiddenSequences != null)
     {
-      if (hiddenSequences[i] != null && hiddenSequences[i] == seq)
+      for (int i = 0; i < hiddenSequences.length; i++)
       {
-        return true;
+        if (hiddenSequences[i] != null && hiddenSequences[i] == seq)
+        {
+          return true;
+        }
       }
     }