Ignore conversion warning

This squashes a invalid value encountered in arccos warning that gets printed multiple times with bilby_mcmc.

bilby/gw/conversion.py

@@ -251,7 +251,8 @@ def convert_to_lal_binary_black_hole_parameters(parameters):
     for angle in ['tilt_1', 'tilt_2', 'theta_jn']:
         cos_angle = str('cos_' + angle)
         if cos_angle in converted_parameters.keys():
-            converted_parameters[angle] = np.arccos(converted_parameters[cos_angle])
+            with np.errstate(invalid="ignore"):
+                converted_parameters[angle] = np.arccos(converted_parameters[cos_angle])
 
     if "delta_phase" in original_keys:
         with np.errstate(invalid="ignore"):