Avoid crash >4 channels in power supply
When >4 power supply channels are defined, GITPHT crashes at the startup with:
Traceback (most recent call last):
File "/home/thermal/GIPHT/oct23_2/gipht/Dialog/Monitor.py", line 98, in run
self.canvas.updateCanvas()
File "/home/thermal/GIPHT/oct23_2/gipht/Dialog/Monitor.py", line 141, in updateCanvas
self.axL.plot(self.x[index], values, color = 'b', linewidth = 0.8, linestyle = styleList[index], marker = '.', markersize = 3)
IndexError: list index out of range
This trivial fix solves the problem.