Add a reduced test-case for issue 6151

Re: issue 6151 and PR 6193.

*Note:* Since this is a `load` test, `makeref` won't be necessary.

test/pdfs/.gitignore

@@ -73,6 +73,7 @@
 !issue4875.pdf
 !issue4881.pdf
 !issue5994.pdf
+!issue6151.pdf
 !rotated.pdf
 !issue1249.pdf
 !issue1171.pdf

test/pdfs/issue6151.pdf

@@ -0,0 +1,67 @@
+%PDF-1.7
+%âãÏÓ
+1 0 obj 
+<<
+/Pages 2 0 R
+/Type /Catalog
+>>
+endobj 
+2 0 obj 
+<<
+/Kids [3 0 R]
+/Count 1
+/Type /Pages
+>>
+endobj 
+3 0 obj 
+<<
+/Parent 2 0 R
+/MediaBox [0 0 200 50]
+/Resources 
+<<
+/Font 
+<<
+/Lorem#20ipsum#20dolor#20sit#20amet,#20consectetur#20adipiscing#20elit.#20Fusce#20ac#20tempor#20erat,#20eu#20vehicula#20ligula.#20Curabitur#20pretium#20suscipit#20pellentesque. 4 0 R
+>>
+>>
+/Contents 5 0 R
+/Type /Page
+>>
+endobj 
+4 0 obj 
+<<
+/BaseFont /Times-Roman
+/Subtype /Type1
+/Encoding /WinAnsiEncoding
+/Type /Font
+>>
+endobj 
+5 0 obj 
+<<
+/Length 214
+>>
+stream
+BT
+10 20 TD
+/Lorem#20ipsum#20dolor#20sit#20amet,#20consectetur#20adipiscing#20elit.#20Fusce#20ac#20tempor#20erat,#20eu#20vehicula#20ligula.#20Curabitur#20pretium#20suscipit#20pellentesque. 20 Tf
+(Issue 6151) Tj
+ET
+
+endstream 
+endobj xref
+0 6
+0000000000 65535 f 
+0000000015 00000 n 
+0000000066 00000 n 
+0000000125 00000 n 
+0000000427 00000 n 
+0000000528 00000 n 
+trailer
+
+<<
+/Root 1 0 R
+/Size 6
+>>
+startxref
+795
+%%EOF

test/test_manifest.json

@@ -1773,6 +1773,13 @@
        "link": false,
        "type": "eq"
     },
+    {  "id": "issue6151",
+       "file": "pdfs/issue6151.pdf",
+       "md5": "926f8c6b25e6f0978759f7947d70e079",
+       "rounds": 1,
+       "link": false,
+       "type": "load"
+    },
     {  "id": "blendmode",
       "file": "pdfs/blendmode.pdf",
       "md5": "5a86e7e9333e93c58abc3f382e1e6ea2",