OWFile: Don't report an error on empty URL

Orange/widgets/data/owfile.py

@@ -257,7 +257,13 @@ def browse_file(self, in_demos=False):
 
     # Open a file, create data from it and send it over the data channel
     def load_data(self):
+        self.editor_model.set_domain(None)
         self.reader = self._get_reader()
+        if not self.reader:
+            self.data = None
+            self.send("Data", None)
+            self.info.setText("No data.")
+            return
         self._update_sheet_combo()
 
         errors = []
@@ -296,7 +302,9 @@ def _get_reader(self):
                 reader.select_sheet(self.recent_paths[0].sheet)
             return reader
         elif self.source == self.URL:
-            return UrlReader(self.url_combo.currentText())
+            url = self.url_combo.currentText().strip()
+            if url:
+                return UrlReader(url)
 
     def _update_sheet_combo(self):
         if len(self.reader.sheets) < 2:

Orange/widgets/utils/domaineditor.py

@@ -55,14 +55,17 @@ def discrete_value_display(value_list):
             return result
 
         self.modelAboutToBeReset.emit()
-        self.variables[:] = self.original = [
-            [var.name, type(var), place,
-             discrete_value_display(var.values) if var.is_discrete else "",
-             may_be_numeric(var)]
-            for place, vars in enumerate(
-                (domain.attributes, domain.class_vars, domain.metas))
-            for var in vars
-        ]
+        if domain is None:
+            self.variables.clear()
+        else:
+            self.variables[:] = self.original = [
+                [var.name, type(var), place,
+                 discrete_value_display(var.values) if var.is_discrete else "",
+                 may_be_numeric(var)]
+                for place, vars in enumerate(
+                    (domain.attributes, domain.class_vars, domain.metas))
+                for var in vars
+            ]
         self.modelReset.emit()
 
     def reset(self):