Skip mapping of CIDFontType2 glyphs in fonts with a |IdentityToUnicodeMap|, unless |properties.widths| is defined for the glyph

Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1142033.
Also fixes issue 5874.

test/pdfs/.gitignore

@@ -7,6 +7,7 @@
 !issue2391-2.pdf
 !issue5801.pdf
 !issue5972.pdf
+!issue5874.pdf
 !filled-background.pdf
 !ArabicCIDTrueType.pdf
 !ThuluthFeatures.pdf

test/pdfs/bug1142033.pdf.link

@@ -0,0 +1 @@
+https://bug1142033.bugzilla.mozilla.org/attachment.cgi?id=8597714

test/test_manifest.json

@@ -947,6 +947,21 @@
       "link": true,
       "type": "load"
     },
+    {  "id": "bug1142033",
+       "file": "pdfs/bug1142033.pdf",
+       "md5": "1d9afd397e89a0f52c056f449ec93daa",
+       "rounds": 1,
+       "lastPage": 1,
+       "link": true,
+       "type": "eq"
+    },
+    {  "id": "issue5874",
+       "file": "pdfs/issue5874.pdf",
+       "md5": "25922edf223aa91bc259663d0a34a6ab",
+       "rounds": 1,
+       "link": false,
+       "type": "eq"
+    },
     {  "id": "S2-eq",
        "file": "pdfs/S2.pdf",
        "md5": "d0b6137846df6e0fe058f234a87fb588",