DevTools: _base64ToSize doesn't check content param for null.

Source/devtools/front_end/source_frame/ImageView.js

 /*
  * Copyright (C) 2007, 2008 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 75 matching lines @@
                 infoListElement.createChild("dt").textContent = imageProperties[i].name;
                 infoListElement.createChild("dd").textContent = imageProperties[i].value;
             }
             infoListElement.createChild("dt").textContent = WebInspector.UIString("URL");
             infoListElement.createChild("dd").appendChild(WebInspector.linkifyURLAsNode(this._url, undefined, undefined, true /* externalResource */));
             this._container.appendChild(infoListElement);
         }
         this._imagePreviewElement = imagePreviewElement;
     },
 
+    /**
+     * @param {?string} content
+     * @return {number}
+     */
     _base64ToSize: function(content)
     {
-        if (!content.length)
+        if (!content || !content.length)
             return 0;
         var size = (content.length || 0) * 3 / 4;
         if (content.length > 0 && content[content.length - 1] === "=")
             size--;
         if (content.length > 1 && content[content.length - 2] === "=")
             size--;
         return size;
     },
 
     _contextMenu: function(event)
@@ skipping 16 matching lines @@
         InspectorFrontendHost.copyText(this._url);
     },
 
     _openInNewTab: function()
     {
         InspectorFrontendHost.openInNewTab(this._url);
     },
 
     __proto__: WebInspector.VBox.prototype
 }