Fix how patterns are applied to image mask objects.

Note, this only really fixes Radial/Axial shading patterns with masks.
I'm guessing tiling patterns and mesh patterns would also be broken
if applied like the test pdf. Hopefully I'll have some time to make
test cases for the other shadings.

Fixes #13372

test/pdfs/.gitignore

@@ -406,6 +406,7 @@
 !issue13193.pdf
 !annotation-underline-without-appearance.pdf
 !issue269_2.pdf
+!issue13372.pdf
 !annotation-strikeout.pdf
 !annotation-strikeout-without-appearance.pdf
 !annotation-squiggly.pdf

test/test_manifest.json

@@ -1566,6 +1566,12 @@
        "rounds": 1,
        "type": "eq"
     },
+    {  "id": "issue13372",
+       "file": "pdfs/issue13372.pdf",
+       "md5": "0bc5329623fd554174c5e7653f904e28",
+       "rounds": 1,
+       "type": "eq"
+    },
     {  "id": "simpletype3font-text",
        "file": "pdfs/simpletype3font.pdf",
        "md5": "b374c7543920840c61999e9e86939f99",