Fixed ZeroDivisionError in thumbnail

Author: radarhere

Tests/test_image_thumbnail.py

@@ -63,6 +63,12 @@ def test_aspect():
     assert im.size == (75, 23)  # ratio is 3.260869565217
 
 
+def test_division_by_zero():
+    im = Image.new("L", (200, 2))
+    im.thumbnail((75, 75))
+    assert im.size == (75, 1)
+
+
 def test_float():
     im = Image.new("L", (128, 128))
     im.thumbnail((99.9, 99.9))

src/PIL/Image.py

@@ -2277,7 +2277,9 @@ def round_aspect(number, key):
         if x / y >= aspect:
             x = round_aspect(y * aspect, key=lambda n: abs(aspect - n / y))
         else:
-            y = round_aspect(x / aspect, key=lambda n: abs(aspect - x / n))
+            y = round_aspect(
+                x / aspect, key=lambda n: 0 if n == 0 else abs(aspect - x / n)
+            )
         size = (x, y)
 
         box = None