commit 51b92d1c9b8cd8710fc1b7e322d664823843a115
Author: Leszek Koltunski <leszek@koltunski.pl>
Date:   Sat Jul 2 13:41:03 2022 +0200

    fix for a crasher.

diff --git a/src/main/java/org/distorted/library/mesh/DeferredJobs.java b/src/main/java/org/distorted/library/mesh/DeferredJobs.java
index fc37d2e..868afec 100644
--- a/src/main/java/org/distorted/library/mesh/DeferredJobs.java
+++ b/src/main/java/org/distorted/library/mesh/DeferredJobs.java
@@ -159,22 +159,25 @@ public class DeferredJobs
       mJob      = job;
       }
 
-    void execute()
+    synchronized void execute()
       {
-      JobNode node;
-      int numPrev = mPrevJobs.size();
-
-      for(int i=0; i<numPrev; i++)
+      if( mPrevJobs!=null )
         {
-        node = mPrevJobs.get(0);  // removeNode() rips the executed job out, thus the 0
-        node.execute();
-        }
+        JobNode node;
+        int numPrev = mPrevJobs.size();
+
+        for(int i=0; i<numPrev; i++)
+          {
+          node = mPrevJobs.get(0);  // removeNode() rips the executed job out, thus the 0
+          node.execute();
+          }
 
-      removeNode(this);
-      mJob.execute();
+        removeNode(this);
+        mJob.execute();
+        }
       }
 
-    void clear()
+    synchronized void clear()
       {
       mPrevJobs.clear();
       mPrevJobs = null;