Fix docs for panics of var_axis and std_axis

Author: jturner314

src/numeric/impl_numeric.rs

@@ -164,7 +164,7 @@ impl<A, S, D> ArrayBase<S, D>
     /// ```
     ///
     /// **Panics** if `ddof` is greater than or equal to the length of the
-    /// axis, if `axis` is out of bounds, or if the length of the axis is zero.
+    /// axis or if `axis` is out of bounds.
     ///
     /// # Example
     ///
@@ -228,7 +228,7 @@ impl<A, S, D> ArrayBase<S, D>
     /// ```
     ///
     /// **Panics** if `ddof` is greater than or equal to the length of the
-    /// axis, if `axis` is out of bounds, or if the length of the axis is zero.
+    /// axis or if `axis` is out of bounds.
     ///
     /// # Example
     ///

tests/array.rs

@@ -816,10 +816,9 @@ fn var_axis_bad_dof() {
 }
 
 #[test]
-#[should_panic]
 fn var_axis_empty_axis() {
     let a = array![[], []];
-    a.var_axis(Axis(1), 0.);
+    a.var_axis(Axis(1), -1.);
 }
 
 #[test]
@@ -830,10 +829,9 @@ fn std_axis_bad_dof() {
 }
 
 #[test]
-#[should_panic]
 fn std_axis_empty_axis() {
     let a = array![[], []];
-    a.std_axis(Axis(1), 0.);
+    a.std_axis(Axis(1), -1.);
 }
 
 #[test]