BF: Check for valid Slider units on compile script.

Author: dvbridges

psychopy/experiment/components/slider/__init__.py

@@ -197,6 +197,10 @@ def __init__(self, exp, parentName,
     def writeInitCode(self, buff):
 
         inits = getInitVals(self.params)
+        # check units
+        if inits['units'].val == 'from exp settings':
+            inits['units'].val = None
+
         # build up an initialization string for Slider():
         initStr = ("{name} = visual.Slider(win=win, name='{name}',\n"
                    "    size={size}, pos={pos}, units={units},\n"