fixed case when font cannot be found

fonts.js

@@ -69,7 +69,11 @@ var Fonts = (function Fonts() {
         var sizes = current.sizes;
         if (!(measureCache = sizes[size]))
           measureCache = sizes[size] = Object.create(null);
+      } else {
+        charsCache = null;
+        measureCache = null
       }
+
       ctx.font = (size * kScalePrecision) + 'px "' + fontName + '"';
     },
     charsToUnicode: function fonts_chars2Unicode(chars) {

pdf.js

@@ -3930,10 +3930,12 @@ var CanvasGraphics = (function() {
         text = Fonts.charsToUnicode(text);
         this.ctx.translate(this.current.x, -1 * this.current.y);
 
-        var font = Fonts.lookupById(this.current.font.id);
-        if (font && font.properties.textMatrix)
-          this.ctx.transform.apply(this.ctx, font.properties.textMatrix);
-
+        var font = this.current.font;
+        if (font) {
+          var fontInfo = Fonts.lookupById(font.id);
+          if (fontInfo && fontInfo.properties.textMatrix)
+            this.ctx.transform.apply(this.ctx, fontInfo.properties.textMatrix);
+        }
         this.ctx.fillText(text, 0, 0);
         this.current.x += Fonts.measureText(text);
       }