say: Fix a bug where SayNumber in Polish tries to play incorrect sound.

This change fixes a bug where calling SayNumber with a number divisible by
100 using the Polish language would cause the code to attempt to play a
sound file with an empty name.

(closes issue ASTERISK-23509)
Reported by: zvision

Review: https://reviewboard.asterisk.org/r/3378/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/1.8@411243 f38db490-d61c-443f-a65b-d21fe96a405b