download_along plugin throws exceptions if no osm data is downloaded before

[Larry0ua]

Please correct me if this bug is already reported.

What steps will reproduce the problem?

1. Install download_along plugin, restart JOSM.
2. Open gpx file (attached to the ticket)
3. Run plugin by menu item

Expected - area is downloaded

Current behavior - error message is shown.

Repository Root: http://josm.openstreetmap.de/svn
Build-Date: 2010-12-31 02:31:28
Last Changed Author: bastiK
Revision: 3751
Repository UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
URL: http://josm.openstreetmap.de/svn/trunk
Last Changed Date: 2010-12-30 16:31:05 +0100 (Thu, 30 Dec 2010)
Last Changed Rev: 3751

Identification: JOSM/1.5 (3751 uk)
Memory Usage: 27 MB / 247 MB (2 MB allocated, but free)
Java version: 1.6.0_23, Sun Microsystems Inc., Java HotSpot(TM) Client VM
Operating system: Windows 7

Plugin: alignways (24815)
Plugin: download_along (22427)
Plugin: restart (24396)

java.lang.NullPointerException
	at org.openstreetmap.josm.plugin.download_along.DownloadAlong$DownloadAlongAction.actionPerformed(DownloadAlong.java:63)
	at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
	at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
	at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
	at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
	at javax.swing.AbstractButton.doClick(Unknown Source)
%0

[Nakor]

The plugin is meant to download data along OSM ways. Therefore the plugin should be available only in an OSM data layer. I fixed it so that it is only available in OSM data layers (not in GPX layer).