NPE race condition alert - see JAL-661

diff --git a/src/jalview/analysis/AAFrequency.java b/src/jalview/analysis/AAFrequency.java
index 4bff6ef..31cb7ad 100755 (executable)
--- a/src/jalview/analysis/AAFrequency.java
+++ b/src/jalview/analysis/AAFrequency.java
@@ -105,6 +105,11 @@ public class AAFrequency
 
       for (j = 0; j < jSize; j++)
       {
+        if (sequences[j]==null)
+        {
+          System.err.println("WARNING: Consensus skipping null sequence - possible race condition.");
+          continue;
+        }
         seq = sequences[j].getSequence();
         if (seq.length > i)
         {