Thanks for th fast answer :D
Solution: patch a Javascript file in the extension directory
\extensions\{31513E58-F253-47ad-86DB-D5F21E905429}\components\minimizeToTrayCmdLine.js
--
there, add a "return;" statement, immediatly after the function call:
cmdLineTest.prototype = {
return;
/* nsICommandLineHandler */
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it's some buggy code for the unsupported turbo mode, it's unused in Sunbird