MSP430 LCD Interfacing via I2C
The code is obviously missing comments what it does. If it did have comments what it does or what it is supposed to do, it would be more clear to find out what's wrong.
First of all the transmit data pointer is initialized to null, so it is sending garbage data instead of data from the transmit data array.
Second problem is that the array contains only command nybbles that must be sent to LCD. They are just loaded to GPIO expander data pins, but the LCD RS, RW and E lines are not set at any point for each command nybble, so the commands are not strobed to the LCD.