Update timestamps for the special process scans at startup also

Resolves https://github.com/htop-dev/htop/issues/592

ProcessList.c

@@ -35,9 +35,11 @@ ProcessList* ProcessList_init(ProcessList* this, const ObjectClass* klass, Users
 
    // set later by platform-specific code
    this->cpuCount = 0;
-
    this->monotonicMs = 0;
 
+   // always maintain valid realtime timestamps
+   Platform_gettime_realtime(&this->realtime, &this->realtimeMs);
+
 #ifdef HAVE_LIBHWLOC
    this->topologyOk = false;
    if (hwloc_topology_init(&this->topology) == 0) {