Ensure that EvaluatorPreprocessor.opMap has a null-prototype (issue 17554)

This accidentally regressed in PR 16956, sorry about that!

test/pdfs/.gitignore

@@ -300,6 +300,7 @@
 !helloworld-bad.pdf
 !zerowidthline.pdf
 !colorspace_cos.pdf
+!issue17554.pdf
 !issue13242.pdf
 !js-colors.pdf
 !annotation-line-without-appearance-empty-Rect.pdf

test/pdfs/issue17554.pdf

@@ -0,0 +1,71 @@
+%PDF-1.4
+%%EOF
+
+6 0 obj
+<<
+ /Type /Catalog
+ /Pages 5 0 R
+>>
+endobj
+
+1 0 obj
+<<
+ /Type /Page
+ /Parent 5 0 R
+ /MediaBox [ 0 0 612 792 ]
+ /Resources 3 0 R
+ /Contents 2 0 R
+>>
+endobj
+
+4 0 obj
+<<
+ /Type /Font
+ /Subtype /Type1
+ /Name /F1
+ /BaseFont/Helvetica
+>>
+endobj
+
+2 0 obj
+<<
+ /Length 53
+>>
+stream
+toString
+endstream
+endobj
+
+5 0 obj
+<<
+ /Type /Pages
+ /Kids [ 1 0 R ]
+ /Count 1
+>>
+endobj
+
+3 0 obj
+<<
+ /ProcSet[/PDF/Text]
+ /Font <</F1 4 0 R >>
+>>
+endobj
+
+xref
+0 7
+0000000000 65535 f
+0000000060 00000 n
+0000000228 00000 n
+0000000424 00000 n
+0000000145 00000 n
+0000000333 00000 n
+0000000009 00000 n
+trailer
+<<
+ /Size 7
+ /Root 6 0 R
+>>
+startxref
+488
+%%EOF
+

test/test_manifest.json

@@ -8762,6 +8762,13 @@
       }
     }
   },
+  {
+    "id": "issue17554",
+    "file": "pdfs/issue17554.pdf",
+    "md5": "09607e5c6007b28b4e75bf8c38a60de3",
+    "rounds": 1,
+    "type": "load"
+  },
   {
     "id": "freetexts-delete-editor-print",
     "file": "pdfs/freetexts.pdf",