Fix FancyArrow rendering for zero-length arrows (matplotlib#30243)

* WIP: changed FancyArrow empty logic

* Update test_patches.py

* Update test_patches.py

* Fix crash when drawing FancyArrow with zero length

* Update patches.py

* Delete .python-version

Author: nrnavaneet

lib/matplotlib/patches.py

@@ -1538,7 +1538,7 @@ def _make_verts(self):
             length = distance
         else:
             length = distance + head_length
-        if not length:
+        if np.size(length) == 0:
             self.verts = np.empty([0, 2])  # display nothing if empty
         else:
             # start by drawing horizontal arrow, point at (0, 0)

lib/matplotlib/tests/test_patches.py

@@ -1093,3 +1093,9 @@ def test_facecolor_none_edgecolor_force_edgecolor():
     rcParams['patch.edgecolor'] = 'red'
     rect = Rectangle((0, 0), 1, 1, facecolor="none")
     assert mcolors.same_color(rect.get_edgecolor(), rcParams['patch.edgecolor'])
+
+
+def test_empty_fancyarrow():
+    fig, ax = plt.subplots()
+    arrow = ax.arrow([], [], [], [])
+    assert arrow is not None