data_view: suppress error when nothing selected.

dstat_interface/interface/data_view.py

@@ -47,7 +47,12 @@ class DataPage(object):
         
     def combobox_changed(self, object):
         """Switch displayed data buffer."""
-        self.textview.set_buffer(self.buffers[self.combobox.get_active_id()])
+        try:
+            self.textview.set_buffer(
+                self.buffers[self.combobox.get_active_id()]
+            )
+        except KeyError:
+            pass
         
 class InfoPage(object):
     def __init__(self, notebook, name="Info"):