Silence FileNotFoundException

[naoliv]

When starting JOSM with an enabled style that isn't available we can see this:

2017-10-24 20:27:39.690 WARNING: Failed to load Mappaint styles from '/tmp/newnodes.mapcss'. Exception was: java.io.FileNotFoundException: /tmp/newnodes.mapcss (No such file or directory)
2017-10-24 20:27:39.691 SEVERE: java.io.FileNotFoundException: /tmp/newnodes.mapcss (No such file or directory)
java.io.FileNotFoundException: /tmp/newnodes.mapcss (No such file or directory)
	at java.base/java.io.FileInputStream.open0(Native Method)
	at java.base/java.io.FileInputStream.open(FileInputStream.java:196)
	at java.base/java.io.FileInputStream.<init>(FileInputStream.java:139)
	at org.openstreetmap.josm.io.CachedFile.getInputStream(CachedFile.java:220)
	at org.openstreetmap.josm.gui.mappaint.mapcss.MapCSSStyleSource.getSourceInputStream(MapCSSStyleSource.java:522)
	at org.openstreetmap.josm.gui.mappaint.mapcss.MapCSSStyleSource.loadStyleSource(MapCSSStyleSource.java:421)
	at org.openstreetmap.josm.gui.mappaint.MapPaintStyles.loadStyleForFirstTime(MapPaintStyles.java:317)
	at org.openstreetmap.josm.gui.mappaint.MapPaintStyles.readFromPreferences(MapPaintStyles.java:310)
	at org.openstreetmap.josm.gui.preferences.map.MapPaintPreference.initialize(MapPaintPreference.java:188)
	at org.openstreetmap.josm.Main$InitializationTask.call(Main.java:604)
	at org.openstreetmap.josm.Main$InitializationTask.call(Main.java:583)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
	at java.base/java.lang.Thread.run(Thread.java:844)

Since JOSM already warns us with 2017-10-24 20:27:39.690 WARNING: Failed to load Mappaint styles from '/tmp/newnodes.mapcss'. Exception was: java.io.FileNotFoundException: /tmp/newnodes.mapcss (No such file or directory), couldn't the exception be simply silenced?

JOSM:

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2017-10-23 00:30:41 +0200 (Mon, 23 Oct 2017)
Revision:13034
Build-Date:2017-10-23 01:33:19
URL:http://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (13034 pt_BR) Linux Debian GNU/Linux unstable (sid)
Memory Usage: 544 MB / 3072 MB (139 MB allocated, but free)
Java version: 9-Debian+0-9b181-4, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: :0.0 1920x1080
Maximum Screen Size: 1920x1080
Java package: openjdk-9-jre:amd64-9~b181-4
Java ATK Wrapper package: libatk-wrapper-java:all-0.33.3-13
VM arguments: [--illegal-access=warn, --add-modules=java.se.ee, -Dawt.useSystemAAFontSettings=on]

[Don-vip]

In 13037/josm:

fix #15481 - Silence FileNotFoundException