fix 'Unexpected item type' error message

The property declaration check shadowed this error.
An erroneous file like

Appliaction {   // mis-spelled Application
    name: "foo"
}

Yielded the error "undeclared property 'name'", when it
should say "I know nothing about Appliaction".

Change-Id: I20d03b13a3fa02b6539950a50d7bae1c5acbfbac
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>