For some reason I don't understand, the array of mi values mst be a l…

…ist, not a tuple.

When a tuple, this line:
w.setText(mi[r].title)

produces the exception:
Traceback (most recent call last):
  File "C:\CBH_Data\calibre.git\calibre_dev\src\calibre\gui2\preferences\save_template.py", line 63, in do_open_editor
  File "C:\CBH_Data\calibre.git\calibre_dev\src\calibre\gui2\dialogs\template_dialog.py", line 433, in __init__
  File "C:\CBH_Data\calibre.git\calibre_dev\src\calibre\gui2\dialogs\template_dialog.py", line 578, in set_mi
AttributeError: 'tuple' object has no attribute 'title'

src/calibre/gui2/preferences/save_template.py

@@ -53,7 +53,7 @@ def do_open_editor(self):
         from calibre.gui2.ui import get_gui
         db = get_gui().current_db
         view = get_gui().library_view
-        mi = tuple(map(db.new_api.get_proxy_metadata, view.get_selected_ids()[:10]))
+        mi = list(map(db.new_api.get_proxy_metadata, view.get_selected_ids()[:10]))
         if not mi:
             error_dialog(self, _('Must select books'),
                          _('One or more books must be selected so the template '