fix a bug (crashing when set output_flat to True and add_bias equal to False) in Chip.py

ObservationSim/Instrument/Chip/Chip.py

@@ -580,7 +580,7 @@ class Chip(FocalPlane):
             if config["ins_effects"]["add_bias"] == True:
                 biaslevel = self.bias_level
                 overscan = biaslevel-2
-            elif config["ins_effects"]["add_bias"] == True:
+            elif config["ins_effects"]["add_bias"] == False:
                 biaslevel = 0
                 overscan = 0
             darklevel = self.dark_noise*(self.flat_exptime+0.5*self.readout_time)