Issue_89 Plugin Crashes when no WebKit/Native browser exists.

Prevent crash and display message.

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #91 from GordonSmith/Issue_89

Issue_89 Plugin Crashes when no WebKit/Native browser exists.

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>