Fix condition to remove dead code

Fix condition to remove dead code

In current code, speak_data is not null if ttsd_data_get_speak_data() returns error none, so null
check on line #99 ~ #102 would become dead code.

To remove this dead code, this patch fixes the condition to check the result of
ttsd_data_get_speak_data(). And this patch fixes some potential memory leak and enhances the
readability.

Change-Id: Ic8dcf0eea79cb57a4a8ad8cf6afc9d59fcd60e49
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>