I tried to download the C program to my target TM4123GXl and it shows the error, but using tivaware examples it's uploaded correctly. I checked with the Objects folder but it seems empty. Anyone knows why this error occurs. Hope you people can help.
use your windows file explorer to go to the directory shown in your screenshot to check if you really have the led.axf file there. If not, uVision has nothing to flash to your target device.
Rebuilding your project free of error once may generate such a led.axf file for you.