Skip bogus d1 operators in Type3-glyphs (issue 14953)

In the `src/display/canvas.js` code the `d1` operator will be used to set the clipping region, and it obviously cannot be empty since that prevents the Type3-glyph from rendering.

Also, the patch removes an outdated comment; refer to PR 12718.

test/pdfs/.gitignore

@@ -49,6 +49,7 @@
 !issue7426.pdf
 !issue7439.pdf
 !issue7847_radial.pdf
+!issue14953.pdf
 !issue7446.pdf
 !issue7492.pdf
 !issue7544.pdf

test/test_manifest.json

@@ -2058,6 +2058,12 @@
        "rounds": 1,
        "type": "eq"
     },
+    {  "id": "issue14953",
+       "file": "pdfs/issue14953.pdf",
+       "md5": "dd7d6cb92e58d75a0eb8c0476a3bc64a",
+       "rounds": 1,
+       "type": "eq"
+    },
     {  "id": "extgstate-text",
        "file": "pdfs/extgstate.pdf",
        "md5": "001bb4ec04463a01d93aad748361f049",