Iced Tea crashes authenticating using JNLP file from USPTO website

[SRDC]

Ubuntu 17.10
Firefox 58.0.2 64bit & Chromium Version 64.0.3282.140
Iced Tea Web (1.6.2-3.1ubuntu3)

Website: https://ppair.uspto.gov/TruePassWebStart/AuthenticationChooser.html --> Choose "new method."

Click on "New method" --> Firefox attempts to open using IcedTea-Web. Chromium asks if you want to keep the file, then you have to manually click it to open it with IcedTea-Web. As soon as IcedTea-Web reads the file, it issues the error below.

It happens without fail on any login after the first login on a given browser (both Firefox & Chromium). First login works fine, subsequent logins crash. I don't believe any updates were done in between. I purged the cache and downloads folders in case appended numbers were causing problems, and checked the newly downloaded JNLP didn't have any appended numbers.

Website/JNLP authentication works fine on current JRE in Windows.

ERROR: (full error report attached)

net.sourceforge.jnlp.LaunchException: Fatal: Read Error: Could not read or parse the JNLP file. You can try to download this file manually and send it as bug report to IcedTea-Web team.
 at net.sourceforge.jnlp.Launcher.fromUrl(Launcher.java:490)
 at net.sourceforge.jnlp.Launcher.launch(Launcher.java:286)
 at net.sourceforge.jnlp.runtime.JnlpBoot.run(JnlpBoot.java:67)
 at net.sourceforge.jnlp.runtime.Boot.run(Boot.java:245)
 at net.sourceforge.jnlp.runtime.Boot.run(Boot.java:63)
 at java.security.AccessController.doPrivileged(Native Method)
 at net.sourceforge.jnlp.runtime.Boot.main(Boot.java:195)
Caused by: java.io.IOException: java.lang.NullPointerException: name can't be null
 at net.sourceforge.jnlp.JNLPFile.openURL(JNLPFile.java:317)
 at net.sourceforge.jnlp.JNLPFile.<init>(JNLPFile.java:239)
 at net.sourceforge.jnlp.JNLPFile.<init>(JNLPFile.java:214)
 at net.sourceforge.jnlp.JNLPFile.<init>(JNLPFile.java:199)
 at net.sourceforge.jnlp.JNLPFile.<init>(JNLPFile.java:185)
 at net.sourceforge.jnlp.Launcher.fromUrl(Launcher.java:454)
 ... 6 more
Caused by: java.lang.NullPointerException: name can't be null
 at java.io.FilePermission.init(FilePermission.java:191)
 at java.io.FilePermission.<init>(FilePermission.java:277)
 at java.lang.SecurityManager.checkRead(SecurityManager.java:888)
 at java.io.FileInputStream.<init>(FileInputStream.java:127)
 at net.sourceforge.jnlp.JNLPFile.openURL(JNLPFile.java:315)
 ... 11 more

[SRDC (timothy-z)]

This is the JNLP file that is crashing.