JS: execute the 'clear' method from the AWT thread
JS: execute the 'clear' method from the AWT thread

Prevents a possible deadlock between the synchronized EntityPallet methods
'clear' and 'getInstance'.

Signed-off-by: Harry King <409587b9e6671aa0763646191d292852dc49a658@gmail.com>

jaamsim/jaamsim,jaamsim/jaamsim,jaamsim/jaamsim,jaamsim/jaamsim