diff --git a/expert/field.py b/expert/field.py
index 0a9d002..ff46650 100644
--- a/expert/field.py
+++ b/expert/field.py
@@ -24,6 +24,15 @@ from cybertools.composer.report.field import Field
 from loops import util
 
 
+class UrlField(Field):
+
+    renderer = 'target'
+
+    def getDisplayValue(self, row):
+        nv = row.parent.context.view.nodeView
+        return dict(title=self.getValue(row), url=nv.getUrlForTarget(row.context))
+
+
 class TargetField(Field):
 
     renderer = 'target'
diff --git a/expert/report.py b/expert/report.py
index 89a8925..c89a2cd 100644
--- a/expert/report.py
+++ b/expert/report.py
@@ -94,9 +94,10 @@ class ReportInstance(BaseReport):
         crit = self.queryCriteria
         if crit is None:
             return []
-        for k, v in dynaParams.items():
-            if k in crit.parts.keys():
-                crit.parts[k].value = v
+        if dynaParams is not None:
+            for k, v in dynaParams.items():
+                if k in crit.parts.keys():
+                    crit.parts[k].value = v
         parts = Jeep(crit.parts)
         result = list(self.selectObjects(parts))  # may modify parts
         qc = CompoundQueryCriteria(parts)