Fix 0-th power [Bug #17521] (#4047)

Author: marcandre

lib/matrix.rb

@@ -1239,7 +1239,7 @@ def **(exp)
  when Integer
  case
  when exp == 0
- _make_sure_it_is_invertible = inverse
+ raise ErrDimensionMismatch unless square?
  self.class.identity(column_count)
  when exp < 0
  inverse.power_int(-exp)