[Linux?] Arduino IDE starts with a white GUI

This now happened a few times under Linux (Ubuntu 64 bit and Elementary 64 bit, also based on Ubunutu). I start the IDE via desktop icon or command line and the GUI just doesnt display anything but white. It also wont quit, I have to kill (not end, kill!) the task (java) via System Monitor.
Noticed this since 1.6.0 or so. Maybe this bug is in earlier version because I started with Ubuntu when IDE 1.6.0 was up to date.


Luckly it happend when I started the IDE in command line. Here is the output. (nightly of just 15 min ago). (BTW: Java 8 integrated in the IDE works perfect so far. Very good idea!)

```
user@pc:~/Documents/Arduino/arduino-nightly$ sh ./arduino
./arduino: 20: ./arduino: [[: not found
./arduino: 20: ./arduino: ==: not found
./arduino: 20: ./arduino: ==: not found
./arduino: 20: ./arduino: ==: not found
./arduino: 20: ./arduino: ==: not found
Picked up JAVA_TOOL_OPTIONS:

(java:2260): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",

(java:2260): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",

(java:2260): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",

(java:2260): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",

(java:2260): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",
Gtk-Message: Failed to load module "canberra-gtk-module"
Could not find boards.txt in /home/user/Documents/Arduino/sketchbook/hardware/HID/examples. Is it pre-1.5?
Could not find boards.txt in /home/user/Documents/Arduino/sketchbook/hardware/HID/dev. Is it pre-1.5?
Could not find boards.txt in /home/user/Documents/Arduino/sketchbook/hardware/HID.wiki/pictures. Is it pre-1.5?
WARNING: Error loading hardware folder /home/user/Documents/Arduino/sketchbook/hardware/HID.wiki
No valid hardware definitions found in folder HID.wiki.
Board Hoodloader:avr:mtdbu1 doesn't define a 'build.board' preference. Auto-set to: AVR_MTDBU1
Board Hoodloader:avr:hoodloader doesn't define a 'build.board' preference. Auto-set to: AVR_HOODLOADER
Warning: platform.txt from core 'Arduino Hoodloader' contains deprecated compiler.path={runtime.ide.path}/hardware/tools/avr/bin/, automatically converted to compiler.path={runtime.tools.avr-gcc.path}/bin/. Consider upgrading this core.
Warning: platform.txt from core 'Arduino Hoodloader' contains deprecated tools.avrdude.cmd.path={runtime.ide.path}/hardware/tools/avr/bin/avrdude, automatically converted to tools.avrdude.cmd.path={path}/bin/avrdude. Consider upgrading this core.
Warning: platform.txt from core 'Arduino Hoodloader' contains deprecated tools.avrdude.config.path={runtime.ide.path}/hardware/tools/avr/etc/avrdude.conf, automatically converted to tools.avrdude.config.path={path}/etc/avrdude.conf. Consider upgrading this core.
Warning: platform.txt from core 'Arduino Hoodloader' misses property tools.avrdude.path, automatically set to {runtime.tools.avrdude.path}. Consider upgrading this core.
Could not find boards.txt in /home/user/Documents/Arduino/sketchbook/hardware/Hoodloader/dev. Is it pre-1.5?
Could not find boards.txt in /home/user/Documents/Arduino/sketchbook/hardware/HoodLoader2/tools. Is it pre-1.5?
Could not find boards.txt in /home/user/Documents/Arduino/sketchbook/hardware/HoodLoader2/dev. Is it pre-1.5?
Could not find boards.txt in /home/user/Documents/Arduino/sketchbook/hardware/HoodLoader2.wiki/pictures. Is it pre-1.5?
WARNING: Error loading hardware folder /home/user/Documents/Arduino/sketchbook/hardware/HoodLoader2.wiki
No valid hardware definitions found in folder HoodLoader2.wiki.
Warning: platform.txt from core 'SparkFun AVR Boards' contains deprecated compiler.path={runtime.ide.path}/hardware/tools/avr/bin/, automatically converted to compiler.path={runtime.tools.avr-gcc.path}/bin/. Consider upgrading this core.
Warning: platform.txt from core 'SparkFun AVR Boards' contains deprecated tools.avrdude.cmd.path={runtime.ide.path}/hardware/tools/avr/bin/avrdude, automatically converted to tools.avrdude.cmd.path={path}/bin/avrdude. Consider upgrading this core.
Warning: platform.txt from core 'SparkFun AVR Boards' contains deprecated tools.avrdude.config.path={runtime.ide.path}/hardware/tools/avr/etc/avrdude.conf, automatically converted to tools.avrdude.config.path={path}/etc/avrdude.conf. Consider upgrading this core.
Warning: platform.txt from core 'SparkFun AVR Boards' misses property tools.avrdude.path, automatically set to {runtime.tools.avrdude.path}. Consider upgrading this core.
Invalid library found in /home/user/Documents/Arduino/sketchbook/libraries/Nintendo.wiki: /home/user/Documents/Arduino/sketchbook/libraries/Nintendo.wiki
Invalid library found in /home/user/Documents/Arduino/sketchbook/libraries/Nintendo.wiki: /home/user/Documents/Arduino/sketchbook/libraries/Nintendo.wiki
Invalid library found in /home/user/Documents/Arduino/sketchbook/libraries/Nintendo.wiki: /home/user/Documents/Arduino/sketchbook/libraries/Nintendo.wiki
Invalid library found in /home/user/Documents/Arduino/sketchbook/libraries/Nintendo.wiki: /home/user/Documents/Arduino/sketchbook/libraries/Nintendo.wiki
^C^C^C^C^C^C^C^C^Z
```

Start by reproducing the blank, non-terminating GUI on the reported Ubuntu-based systems using the ./arduino launcher and the command-line output shown. Inspect the launcher diagnostics and Java/GTK startup messages, while checking whether the sketchbook hardware and library warnings affect startup. Done means the IDE displays its interface and exits normally without requiring the Java process to be killed.

Written by the indexing model from the issue text.