Revert changes from Flavio: https://git.eclipse.org/r/#/c/43462/ because
of Bug 462928
diff --git a/plugins/org.eclipse.bpmn2.modeler.ui/src/org/eclipse/bpmn2/modeler/ui/editor/BPMN2Editor.java b/plugins/org.eclipse.bpmn2.modeler.ui/src/org/eclipse/bpmn2/modeler/ui/editor/BPMN2Editor.java
index 5f12642..4fb73f4 100644
--- a/plugins/org.eclipse.bpmn2.modeler.ui/src/org/eclipse/bpmn2/modeler/ui/editor/BPMN2Editor.java
+++ b/plugins/org.eclipse.bpmn2.modeler.ui/src/org/eclipse/bpmn2/modeler/ui/editor/BPMN2Editor.java
@@ -388,7 +388,7 @@
 				// If the bpmn file was missing DI elements, they would have been added by the importer
 				// so save the file now in case it was changed.
 				saveModelFile();
-			} else {
+			} else if (targetNamespace!=null && !targetNamespace.isEmpty()){
 				modelHandler.getDefinitions().setTargetNamespace(targetNamespace);
 			}