Fix undefined group bounding box

src/display/canvas.js

@@ -1507,10 +1507,11 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
                     group.bbox,
                     currentCtx.mozCurrentTransform);
       // Clip the bounding box to the current canvas.
-      bounds = Util.intersect(bounds, [0,
+      var canvasBounds = [0,
                           0,
                           currentCtx.canvas.width,
-                                       currentCtx.canvas.height]);
+                          currentCtx.canvas.height];
+      bounds = Util.intersect(bounds, canvasBounds) || [0, 0, 0, 0];
       // Use ceil in case we're between sizes so we don't create canvas that is
       // too small and make the canvas at least 1x1 pixels.
       var drawnWidth = Math.max(Math.ceil(bounds[2] - bounds[0]), 1);

test/pdfs/issue3879.pdf.link

@@ -0,0 +1 @@
+http://particuliers.lcl.fr/quotidien/cartes/simplifier_quotidien/carte-visa-cleo/Ressources/pdf/dispositions_generales_cb_cleo.pdf

test/test_manifest.json

@@ -33,6 +33,15 @@
        "type": "load",
        "about": "PDF with undefined stream length."
     },
+    {  "id": "issue3879",
+       "file": "pdfs/issue3879.pdf",
+       "md5": "1cd1f1c3271515a14e65ff2980e14663",
+       "rounds": 1,
+       "link": true,
+       "firstPage": 2,
+       "lastPage": 2,
+       "type": "eq"
+    },
     {  "id": "issue2833",
        "file": "pdfs/issue2833.pdf",
        "md5": "7bc6e17c41586155c188d7408bcb9ab5",