fixes #47402

Rhino 1.7R4 Introduces the Class ConsString to improve String operation performance. (https://developer.mozilla.org/en-US/docs/New_in_Rhino_1.7R4)
This breaks the ScriptEngine Adapter.

The latest Rhino Version bundled with oracle java is Rhino v 1.7R3. Thus, there is no ScriptEngine Adapter for the R4 Version.

This fix should do the job by converting ConsString to String in the Scriptable Getter




git-svn-id: svn://svn.jdownloader.org/jdownloader/trunk@26282 ebf7c1c2-ba36-0410-9fe8-c592906822b4