Added error check for empty appId

:Release Notes:
Check added for setAppProperty for empty appid

:Detailed Notes:

:Testing Performed:
Compiled locally and tested in device

:QA Notes:

:Issues Addressed:
[GF-9613] Getting application property for EMPTY appId as input parameter in
com.palm.preferences/appProperties/getAllAppProperties

Open-webOS-DCO-1.0-Signed-off-by: Yasaswini A Y <yasaswini.ay@lge.com>

Change-Id: I5a66bc27bf060103d210194a8b51bdb0149fdebf
Reviewed-on: https://g2g.palm.com/3329
Reviewed-by: Build Verification
Tested-by: Yasaswini AY <yasaswini.ay@lge.com>
Reviewed-by: Roger Stringer <roger.stringer@lge.com>