Remove editor type selector from File Browser when in 'Operator' mode.

Having that one when opening a file or loading some lib makes absolutely
no sense, and switching that 'temp' editor to some other type can
trigger all kind of funny bugs...

Note that using the shortcuts keys (Shift-F5 etc.) is still possible,
removing those seems a bit more involved. :/

release/scripts/startup/bl_ui/space_filebrowser.py

@@ -28,8 +28,10 @@ class FILEBROWSER_HT_header(Header):
         layout = self.layout
 
         st = context.space_data
+        params = st.params
 
-        layout.template_header()
+        if st.active_operator is None:
+            layout.template_header()
 
         row = layout.row()
         row.separator()
@@ -46,7 +48,6 @@ class FILEBROWSER_HT_header(Header):
         layout.separator()
 
         layout.operator_context = 'INVOKE_DEFAULT'
-        params = st.params
 
         # can be None when save/reload with a file selector open
         if params: