Some Preferences tabs cause JOSM to freeze when not connected to the internet

[anonymous]

What steps will reproduce the problem?

1. While not connected to the internet, open Preferences and click any tab that tries to go to the internet.

What is the expected result?

JOSM should not freeze.

What happens instead?

An exception is shown and JOSM freezes even after the exception message goes away.

Please provide any additional information below. Attach a screenshot if possible.

URL:http://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2016-09-06 00:16:07 +0200 (Tue, 06 Sep 2016)
Build-Date:2016-09-05 22:21:00
Revision:10966
Relative:URL: ^/trunk

Identification: JOSM/1.5 (10966 en) Windows XP 32-Bit
Memory Usage: 123 MB / 989 MB (57 MB allocated, but free)
Java version: 1.8.0_92-b14, Oracle Corporation, Java HotSpot(TM) Client VM
Screen: \Display0 1440x900
Maximum Screen Size: 1440x900

Plugins:
+ download_along (32946)
+ log4j (32699)
+ pbf (32865)
+ routing (32796)
+ turnrestrictions (32796)

[simon04]

In 16964/josm:

fix #13586, see #18162 - Preferences: do not update source entries automatically when --offline=CACHE_UPDATES