Allow requested installer package name to be null

Since an installer package name may be null, switch to
TextUtils.equals to allow for this case and to stop
any NullPointerExceptions

Test: adb shell pm install --staged
      /system/app/CaptivePortalLogin/CaptivePortalLogin.apk works
Bug: 145575703

Change-Id: Ic30cc4610884657aaa8415dc96107c7cc3647ce9