This fixes http://code.google.com/p/chromium/issues/detail?id=493, which was a crash in the 3dvia plugin. A script on the page tries to interact with the plugin by obtain its npobject. The plugin's does not implement the corresponding NPP_GetValue function correctly and returns NPERR_NO_ERROR  without filling in the NPObject pointer passed in. 
This fixes http://code.google.com/p/chromium/issues/detail?id=493, which
was a crash in the 3dvia plugin. A script on the page tries to interact
with the plugin by obtain its npobject. The plugin's does not implement the
corresponding NPP_GetValue function correctly and returns NPERR_NO_ERROR 
without filling in the NPObject pointer passed in. 

The fix is to initialize the NPObject pointer on the stack to NULL and check
for this along with the error check.

Review URL: http://codereview.chromium.org/212

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@1692 0039d316-1c4b-4281-b951-d872f2087c98

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