Ensure that the params parameter of the PredictorStream is a dictionary (issue 7200)

Fixes 7200.

src/core/stream.js

@@ -39,6 +39,7 @@ var createObjectURL = sharedUtil.createObjectURL;
 var shadow = sharedUtil.shadow;
 var warn = sharedUtil.warn;
 var Dict = corePrimitives.Dict;
+var isDict = corePrimitives.isDict;
 var Jbig2Image = coreJbig2.Jbig2Image;
 var JpegImage = coreJpg.JpegImage;
 var JpxImage = coreJpx.JpxImage;
@@ -680,6 +681,9 @@ var FlateStream = (function FlateStreamClosure() {
 
 var PredictorStream = (function PredictorStreamClosure() {
   function PredictorStream(str, maybeLength, params) {
+    if (!isDict(params)) {
+      return str; // no prediction
+    }
     var predictor = this.predictor = params.get('Predictor') || 1;
 
     if (predictor <= 1) {

test/pdfs/.gitignore

@@ -23,6 +23,7 @@
 !issue7020.pdf
 !issue7101.pdf
 !issue7115.pdf
+!issue7200.pdf
 !filled-background.pdf
 !ArabicCIDTrueType.pdf
 !ThuluthFeatures.pdf

test/test_manifest.json

@@ -1270,6 +1270,13 @@
        "rounds": 1,
        "type": "eq"
     },
+    {  "id": "issue7200",
+       "file": "pdfs/issue7200.pdf",
+       "md5": "ddae17424ea23930eecf8b612a66ed0f",
+       "link": false,
+       "rounds": 1,
+       "type": "eq"
+    },
     {  "id": "pr4606",
        "file": "pdfs/pr4606.pdf",
        "md5": "6574fde2314648600056bd0e229df98c",