Fixed `customPlaceholderText` in Message Center. Fixes IOS-603
Fixed `customPlaceholderText` in Message Center.
Fixes IOS-603

sahara108/apptentive-ios,Jawbone/apptentive-ios,hibu/apptentive-ios,hibu/apptentive-ios,apptentive/apptentive-ios,hibu/apptentive-ios,apptentive/apptentive-ios,apptentive/apptentive-ios,ALHariPrasad/apptentive-ios,Jawbone/apptentive-ios,sahara108/apptentive-ios,ALHariPrasad/apptentive-ios