Fixed FMLRelaunchLog's Newline Handling

System.out.println("\n") causes currentMessage to start with a newline character, which means idx will always be 0 from then on. Therefore if idx is 0 messages must still be logged, otherwise no more messages sent to stdout will be logged and they will just accumulate in currentMessage.
Merge pull request #208 from jrtc27/patch-1

Fixed FMLRelaunchLog's Newline Handling