Update delay accounting to use NAN on error

linux/LinuxProcess.c

@@ -182,7 +182,7 @@ bool LinuxProcess_setIOPriority(LinuxProcess* this, Arg ioprio) {
 
 #ifdef HAVE_DELAYACCT
 void LinuxProcess_printDelay(float delay_percent, char* buffer, int n) {
-  if (delay_percent == -1LL) {
+  if (isnan(delay_percent)) {
     xSnprintf(buffer, n, " N/A  ");
   } else {
     xSnprintf(buffer, n, "%4.1f  ", delay_percent);

linux/LinuxProcessList.c

@@ -681,9 +681,9 @@ static void LinuxProcessList_readDelayAcctData(LinuxProcessList* this, LinuxProc
    }
 
    if (nl_send_sync(this->netlink_socket, msg) < 0) {
-      process->swapin_delay_percent = -1LL;
+      process->swapin_delay_percent = NAN;
-      process->blkio_delay_percent = -1LL;
+      process->blkio_delay_percent = NAN;
-      process->cpu_delay_percent = -1LL;
+      process->cpu_delay_percent = NAN;
       return;
    }