Potential jump-misses-init issue in ncgenl.c

[WardF]

While investigating #2486 I had cause to look into the details of -std=c99. I was able to detecting a potential issue in ncgenl.c when compiling with -Werror=jump-misses-init. I am curious to see if correcting this potentially corrects the error observed by the Julia build team in #2486, which was resolved by removing "-std=c99" from their CFLAGS. It's a shot in the dark, but worth fixing/testing.