Guard QML-specific handling of value type property access
Guard QML-specific handling of value type property access

When using QJSEngine, there is no QDeclarativeEngine
associated with the QV8Engine, so check if it's there first.

This was causing the QJS qobject bindings autotest to crash.

Change-Id: If2c1d414d615bfbe93580d06555f5c17b0e41eef
Reviewed-on: http://codereview.qt.nokia.com/2845
Reviewed-by: Qt Sanity Bot <5581206bb7e0307f0d99eb71898ae6b694149ca5@ovi.com>
Reviewed-by: Aaron Kennedy <087c9f3fe24ea980d31d6a327c000f1b04b5a585@nokia.com>

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