allow exception to flow out rather than losing it due to an NPE

org.aspectj.ajdt.core/src/org/aspectj/ajdt/internal/core/builder/AjBuildManager.java

@@ -344,7 +344,7 @@ public class AjBuildManager implements IOutputClassFileNameProvider,IBinarySourc
         	}
             ret = !handler.hasErrors();
             if (getBcelWorld()!=null) getBcelWorld().tidyUp();
-            getWeaver().tidyUp();
+            if (getWeaver()!=null) getWeaver().tidyUp();
             // bug 59895, don't release reference to handler as may be needed by a nested call
             //handler = null;
         }