compiler warning - uninitialized use

[bondhugula]

With GCC 8.3.1 (with -Wextra) and the current master tip 261eec0

CC source/pip_dp-maind.o
source/maind.c: In function ‘main’:
source/maind.c:186:27: warning: ‘g’ may be used uninitialized in this function [-Wmaybe-uninitialized]
if(verbose_xx > 0) {fprintf(dump_xx, "hwm %p\n", g);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CCLD pip_dp