Division by zero error in indicators.

[muazhari]

Reproducible:

Suggestion:

• Try to fix it by adding an exception in

  pymoo/pymoo/util/normalization.py

  Lines 57 to 69 in 9d851f4

  	# if both are equal then set the upper bound to none (always the 0 or lower bound will be returned then)
  	xu[xl == xu] = np.nan
  	# store the lower and upper bounds
  	self.xl, self.xu = xl, xu
  	# check out when the input values are nan
  	xl_nan, xu_nan = np.isnan(xl), np.isnan(xu)
  	# now create all the masks that are necessary
  	self.xl_only, self.xu_only = np.logical_and(~xl_nan, xu_nan), np.logical_and(xl_nan, ~xu_nan)
  	self.both_nan = np.logical_and(np.isnan(xl), np.isnan(xu))
  	self.neither_nan = ~self.both_nan

• Try to fix it using epsilon, i.e. norm[norm==0] = np.finfo(norm.dtype).eps