firefox print dialog selects print to file when selecting a non-default printer

STEPS TO REPRODUCE
 1. Open the print dialog with e.g. File → Print or (hamburger icon) → Print → Print
 2. Select a non-default printer
 3. Select one of the tabs in the dialog, e.g. Page Setup

EXPECTED RESULTS
The tab is opened for the selected printer.

ACTUAL RESULTS
The Print to File printer is selected and does not open the tab. The other tabs available in other printers (but not in this virtual printer for Print to File) are missing. Continuing to print will attempt to print to file.

AFFECTS
 * firefox 46.0+build5-0ubuntu0.14.04.2

WORKAROUND
 1. After the Print to File printer is selected, click the Page Setup or Options tabs
 2. Change options as needed
 3. Select the General tab
 4. Reselect the right printer and those settings will be applied
…but note that you can't change anything on other tabs.
 * or install Aurora from the Mozilla Build Team's PPA: https://launchpad.net/~ubuntu-mozilla-daily/+archive/ubuntu/firefox-aurora

NOTES
 * 20 April, I received an update to 45.0.2+build1-0ubuntu0.14.04.1, which was unaffected. There have been no other updates since.
 * 47.0~a2~hg20160412r310537-0ubuntu1~umd1~trusty (Aurora) is unaffected
 * This is on i386 Kubuntu, but neither fact should be relevant.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: firefox 46.0+build5-0ubuntu0.14.04.2
ProcVersionSignature: Ubuntu 4.2.0-34.39~14.04.1-generic 4.2.8-ckt4
Uname: Linux 4.2.0-34-generic x86_64
AddonCompatCheckDisabled: False
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: wxl 10651 F.... pulseaudio
BuildID: 20160425115337
Channel: Unavailable
CurrentDesktop: KDE
Date: Wed Apr 27 10:23:16 2016
Extensions: extensions.sqlite corrupt or missing
ForcedLayersAccel: False
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
IncompatibleExtensions: Unavailable (corrupt or non-existant compatibility.ini or extensions.sqlite)
InstallationDate: Installed on 2013-05-14 (1078 days ago)
InstallationMedia: Kubuntu 13.04 "Raring Ringtail" - Release i386 (20130424)
IpRoute:
 default via 10.23.1.1 dev eth1 proto static
 10.23.1.0/24 dev eth1 proto kernel scope link src 10.23.1.236 metric 1
 192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1
IwConfig:
 eth1 no wireless extensions.

 virbr0 no wireless extensions.

 lo no wireless extensions.
Locales: extensions.sqlite corrupt or missing
MostRecentCrashID: bp-0c2bf835-4be0-4e41-9cc7-9808d2150512
Plugins:
 Skype Buttons for Kopete - /usr/lib/mozilla/plugins/skypebuttons.so (kopete)
 IcedTea-Web Plugin (using IcedTea-Web 1.5.3 (1.5.3-0ubuntu0.14.04.1)) - /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/IcedTeaPlugin.so (icedtea-7-plugin)
 Shockwave Flash - /usr/lib/flashplugin-installer/libflashplayer.so
PrefSources: prefs.js
Profiles: Profile0 (Default) - LastVersion=46.0/20160425115337 (In use)
RelatedPackageVersions:
 kopete 4:4.14.3-0ubuntu1~ubuntu14.04~ppa2
 icedtea-7-plugin 1.5.3-0ubuntu0.14.04.1
RfKill:
 0: hci0: Bluetooth
  Soft blocked: no
  Hard blocked: no
RunningIncompatibleAddons: False
SourcePackage: firefox
SubmittedCrashIDs:
 bp-0c2bf835-4be0-4e41-9cc7-9808d2150512
 bp-170302ae-8534-430b-843c-5b3d62150403
Themes: extensions.sqlite corrupt or missing
UpgradeStatus: Upgraded to trusty on 2015-02-20 (432 days ago)
dmi.bios.date: 07/21/2011
dmi.bios.vendor: Hewlett-Packard
dmi.bios.version: 786F1 v01.32
dmi.board.asset.tag: 2UA8250JJQ
dmi.board.name: 0AA8h
dmi.board.vendor: Hewlett-Packard
dmi.chassis.asset.tag: 2UA8250JJQ
dmi.chassis.type: 4
dmi.chassis.vendor: Hewlett-Packard
dmi.modalias: dmi:bvnHewlett-Packard:bvr786F1v01.32:bd07/21/2011:svnHewlett-Packard:pnHPCompaqdc7800SmallFormFactor:pvr:rvnHewlett-Packard:rn0AA8h:rvr:cvnHewlett-Packard:ct4:cvr:
dmi.product.name: HP Compaq dc7800 Small Form Factor
dmi.sys.vendor: Hewlett-Packard