FIX use specific structuring element in Canny

skimage/filter/_canny.py

@@ -254,7 +254,8 @@ def canny(image, sigma=1., low_threshold=.1, high_threshold=.2, mask=None):
     # Segment the low-mask, then only keep low-segments that have
     # some high_mask component in them
     #
-    labels, count = label(low_mask, np.ndarray((3, 3), bool))
+    strel = np.ones((3, 3), bool)
+    labels, count = label(low_mask, strel)
     if count == 0:
         return low_mask