Importvec loading progress bar blocks prompt dialog indefinitely

[ff5722]

What steps will reproduce the problem?

1. Open an SVG file in JOSM using the Importvec plugin

What is the expected result?

The SVG import dialog is shown and you can choose a curve step number

What happens instead?

An loading screen which never ends is shown. You have to close that loading dialog (which does not interrupt anything) to actually import the svg.

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: 2017-10-29 19:52:48 +0100 (Sun, 29 Oct 2017)
Build-Date:2017-10-29 19:11:19
Revision:13053
Relative:URL: ^/trunk

Identification: JOSM/1.5 (13053 en) Windows 10 64-Bit
OS Build number: Windows 10 Home 1703 (15063)
Memory Usage: 456 MB / 989 MB (105 MB allocated, but free)
Java version: 1.8.0_151-b12, Oracle Corporation, Java HotSpot(TM) Client VM
Screen: \Display0 1280x720
Maximum Screen Size: 1280x720
VM arguments: [-Djava.security.manager, -Djava.security.policy=file:<java.home>\lib\security\javaws.policy, -DtrustProxy=true, -Djnlpx.home=<java.home>\bin, -Djnlpx.origFilenameArg=E:\Box Sync\Desktop\josm.jnlp, -Djnlpx.remove=true, -Djava.util.Arrays.useLegacyMergeSort=true, -Djnlpx.heapsize=256m,1024m, -Djnlpx.splashport=59152, -Djnlpx.jvm=<java.home>\bin\javaw.exe]
Dataset consistency test: No problems found

Plugins:
+ FastDraw (33731)
+ ImportImagePlugin (33563)
+ Mapillary (v1.5.8)
+ PicLayer (33385)
+ apache-commons (33668)
+ apache-http (32699)
+ buildings_tools (33735)
+ ejml (32680)
+ ext_tools (33698)
+ geojson (66)
+ geotools (33380)
+ importvec (33564)
+ jogl (1.1.0)
+ jts (32699)
+ kendzi3d-resources (0.0.1)
+ log4j (32699)
+ opendata (33617)
+ reverter (33572)
+ utilsplugin2 (33742)

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.
- W: No default layer selected, choosing first layer.
- W: No default layer selected, choosing first layer.