Use font's default width even when 0.

Bug 1392647 has a PDF where the default width of the font
is 0. It draws some charcodes that don't have glyphs, but
we were wrongly using the 1000 default width for these
charcodes causing some text to be overlapping.

src/core/evaluator.js

@@ -2083,7 +2083,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
       var defaultVMetrics;
       var i, ii, j, jj, start, code, widths;
       if (properties.composite) {
-        defaultWidth = dict.get('DW') || 1000;
+        defaultWidth = dict.has('DW') ? dict.get('DW') : 1000;
 
         widths = dict.get('W');
         if (widths) {

test/pdfs/.gitignore

@@ -145,6 +145,7 @@
 !pr6531_2.pdf
 !pr7352.pdf
 !bug900822.pdf
+!bug1392647.pdf
 !issue918.pdf
 !issue1905.pdf
 !issue2833.pdf

test/test_manifest.json

@@ -867,6 +867,13 @@
        "link": false,
        "type": "eq"
     },
+    {  "id": "bug1392647",
+       "file": "pdfs/bug1392647.pdf",
+       "md5": "9770ea476630ca7d560b7c39430f8850",
+       "rounds": 1,
+       "link": false,
+       "type": "eq"
+    },
     {  "id": "hudsonsurvey",
        "file": "pdfs/hudsonsurvey.pdf",
        "md5": "bf0e6576a7b6c2fe7485bce1b78e006f",