Hal crashes when a value of 0 is entered for locked.offset_threshold

[jeffmoffitt]

I discovered this bug when I accidentally set locked.offset_threshold to 0. Hal crashed (in a reproducible fashion) and generated the following traceback:
....
sc_library\parameters.py line 317 in toType
return(float(new_value))
ValueError: could not convert string to float

The issue only occurs if one types "0" and then hits return. If you click outside of the edit region, then Qt automatically sets the value to 0.0

[Hazen Babcock]

Should be fixed now.