Make sure None is treated as non-zero

For some reason `argwhere` treats None as zero which fails an existing
test.

Author: lagru

numpy/lib/_function_base_impl.py

@@ -1891,7 +1891,7 @@ def _arg_trim_zeros(filt):
     >>> _arg_trim_zeros(np.array([0, 0, 1, 1, 0]))
     (array([2]), array([3]))
     """
-    nonzero = np.argwhere(filt)
+    nonzero = np.argwhere(filt != 0)
     if nonzero.size == 0:
         start = stop = np.array([], dtype=np.intp)
     else: