--- a/artifacts/src/main/java/org/dive4elements/river/artifacts/sinfo/tkhstate/TkhCalculation.java	Wed Feb 28 17:27:15 2018 +0100
+++ b/artifacts/src/main/java/org/dive4elements/river/artifacts/sinfo/tkhstate/TkhCalculation.java	Wed Feb 28 18:55:39 2018 +0100
@@ -11,6 +11,7 @@
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.List;
 
 import org.apache.commons.lang.math.DoubleRange;
 import org.dive4elements.artifacts.CallContext;
@@ -87,8 +88,11 @@
 
         /* copy all problems */
         final Calculation winfoProblems = waterlevelData.getReport();
-        for (final Problem problem : winfoProblems.getProblems()) {
-            problems.addProblem(problem);
+        final List<Problem> problems2 = winfoProblems.getProblems();
+        if (problems2 != null) {
+            for (final Problem problem : problems2) {
+                problems.addProblem(problem);
+            }
         }
 
         return (WQKms[]) waterlevelData.getData();