FIX: For stride == 1 axes, require len > 1 to determine C/F preference

The issue was that otherwise, this array:
shape: [1, 256]
strides: [1, 256]

Which was "correctly" determined to be F-preference because it's
sliced out of an f-order array. In reality it is discontiguous; every
element is 256 steps from the next. This should have layout None, the
same as this array would have (ignoring 1-len axes).

shape: [256]
strides: [256]

Author: bluss

src/zip/mod.rs

@@ -69,9 +69,9 @@ where
         } else if n > 1 && self.raw_view().reversed_axes().is_standard_layout() {
             Layout::f()
         } else if n > 1 {
-            if self.stride_of(Axis(0)) == 1 {
+            if self.len_of(Axis(0)) > 1 && self.stride_of(Axis(0)) == 1 {
                 Layout::fpref()
-            } else if self.stride_of(Axis(n - 1)) == 1 {
+            } else if self.len_of(Axis(n - 1)) > 1 && self.stride_of(Axis(n - 1)) == 1 {
                 Layout::cpref()
             } else {
                 Layout::none()