pmap: Increase memory allocation failure judgment
Call trace: #0 __vsnprintf_internal #1 (closed) 0x00007f967aedd656 in __GI___snprintf #2 (closed) 0x00005612da28c707 in snprintf #3 (closed) config_read (rc_filename=) at pmap.c:885 #4 (closed) 0x00005612da28b8c0 int main at pmap.c:1144
The above stack is caused by calling a null pointer after the memory allocation fails. Increase the null pointer judgment.
signed-off-by: zhoujie zhoujie133@huawei.com