location-importer.in: Fix dangling variable

This fixes:

Traceback (most recent call last):
  File "/usr/bin/location-importer", line 1607, in <module>
    main()
  File "/usr/bin/location-importer", line 1605, in main
    c.run()
  File "/usr/bin/location-importer", line 140, in run
    ret = args.func(args)
  File "/usr/bin/location-importer", line 1234, in handle_update_overrides
    self._update_overrides_for_spamhaus_drop()
  File "/usr/bin/location-importer", line 1504, in _update_overrides_for_spamhaus_drop
    for sline in t.readlines():
NameError: name 't' is not defined
Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

src/scripts/location-importer.in

@@ -1499,7 +1499,7 @@ class CLI(object):
 			# Iterate through every line, filter comments and add remaining ASNs to
 			# the override table in case they are valid...
 			with self.db.transaction():
-				for sline in t.readlines():
+				for sline in f.readlines():
 					# The response is assumed to be encoded in UTF-8...
 					sline = sline.decode("utf-8")