Error when connecting to COM port

[Casssss]

Hi all,
I am trying to use the GUI_V0_3, I have an arduino MEGA2560 attached that is not yet connected to the printer and I use processing 1.5.1. When I click the connection tab in the interface after converting this warning pops up in the message window:
WARNING: RXTX Version mismatch
Jar version = RXTX-2.2pre1
native lib Version = RXTX-2.1-7

I have followed the steps described in this link and added rxtx-2.1-7-bins-r2.zip to the processing :
https://forum.processing.org/one/topic/how-do-i-install-rxtx-2-2pre1-jar-on-windows-7.html#25080000000981023 but it doesn't seem to change anything.

When I ignore the warning and click the COM port that connects my arduino, the following error comes up:
Exception in thread "Animation Thread" java.lang.ArrayIndexOutOfBoundsException: 1
at Pwdr_GUI_V0_3.startSerial(Pwdr_GUI_V0_3.java:498)
at Pwdr_GUI_V0_3.mouseClicked(Pwdr_GUI_V0_3.java:1056)
at processing.core.PApplet.handleMouseEvent(Unknown Source)
at processing.core.PApplet.dequeueMouseEvents(Unknown Source)
at processing.core.PApplet.handleDraw(Unknown Source)
at processing.core.PApplet.run(Unknown Source)
at java.lang.Thread.run(Thread.java:662)
I have already filled in the correct serial port (COM3) at line 6 of the serial tab.
Is this familiar to anyone?