“Pending” SMS is not sent automatically after airplane mode is turned off with VZW sim card

Rootcause: When airplane mode is on, the network operator is set to empty.
If VZW's assisted dailing for sms feature is enabled, there would be
StringIndexOutOfBoundsException if there is not empty check for network operator.

Bug:18828906

Change-Id: I72b1525a927097d1c70a2d56b0e624508cce73d1