Do not clear tile if not updating the image when seeking

Author: radarhere

Tests/images/comment_after_only_frame.gif

@@ -399,6 +399,11 @@ def test_no_change():
         assert im.is_animated
         assert_image_equal(im, expected)
 
+    with Image.open("Tests/images/comment_after_only_frame.gif") as im:
+        expected = Image.new("P", (1, 1))
+        assert not im.is_animated
+        assert_image_equal(im, expected)
+
 
 def test_eoferror():
     with Image.open(TEST_GIF) as im:

Tests/test_file_gif.py

@@ -185,8 +185,6 @@ def _seek(self, frame, update_image=True):
         if not s or s == b";":
             raise EOFError
 
-        self.tile = []
-
         palette = None
 
         info = {}
@@ -295,6 +293,8 @@ def _seek(self, frame, update_image=True):
         if not update_image:
             return
 
+        self.tile = []
+
         if self.dispose:
             self.im.paste(self.dispose, self.dispose_extent)