Fixed: "Notice: Undefined variable: upgrade_notice ... "

The variable `$upgrade_notice` is never initialized if there is no upgrade notice section which is the case with v1.0 plugins, so it throws the following error:

> `Notice: Undefined variable: upgrade_notice in`
> `/Users/mikeschinkel/Tools/wppm/src/readme-parser/parse-readme.php on line 202`

This patch simply moves the initialization of  `$upgrade_notice` from inside the `if( ... ) { ... }` to just before it.