[kupfer] learn: Don't write an empty register

[Ulrik Sverdrup <usverdrup src gnome org>]

commit 693bde0f8dbd0e70bade88cdb9dda97b8df45747
Author: Ulrik Sverdrup <ulrik sverdrup gmail com>
Date:   Tue Aug 25 13:24:46 2009 +0200

    learn: Don't write an empty register
    
    The empty register might overwrite a good register that we didn't load
    if we had an exception at program launch.

 kupfer/learn.py |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/kupfer/learn.py b/kupfer/learn.py
index d1ecae6..2d2a0a9 100644
--- a/kupfer/learn.py
+++ b/kupfer/learn.py
@@ -98,5 +98,8 @@ def finish():
 	"""
 	Close and save the learning record
 	"""
+	if not _register:
+		pretty.print_debug(__name__, "Not writing empty register")
+		return
 	filepath = config.save_data_file(mnemonics_filename)
 	Learning._pickle_register(_register, filepath)