Occasional segmentation fault when atop is combined with netatop

Even when the number of exited processes via netatop was zero, still
a malloc was issued. In certain circumstances a structure could have
been stored at the address that was returned by malloc, resulting in
a segmentation fault on a subsequent malloc.

Author: Atoptool

netatopif.c

@@ -344,6 +344,9 @@ netatop_exitstore(void)
 	nexitnet = nahp->curseq - lastseq;
 	lastseq  = nahp->curseq;
 
+	if (nexitnet == 0)
+		return 0;
+
 	/*
 	** allocate storage for all exited processes
 	*/