algo: Fix metrics when monitor is not present.

algo/base/SubChain.h

@@ -23,6 +23,7 @@ namespace cbm::algo
     Monitor& GetMonitor() const
     {
       // Need Get-prefix to avoid conflict with Monitor-class name
+      if (!HasMonitor()) throw std::runtime_error("No monitor available");
       return *gsl::make_not_null(fContext)->monitor;
     }
 

algo/global/Reco.cxx

@@ -85,9 +85,11 @@ void Reco::Run(const fles::Timeslice& ts)
 
   xpu::timings ts_times = xpu::pop_timer();
 
+  if (HasMonitor())
     GetMonitor().QueueMetric("cbm_reco", {{"hostname", fles::system::current_hostname()}},
                              {{"tsProcessed", 1}, {"bytesProcessed", ts_utils::SizeBytes(ts)}});
 
+
   PrintTimings(ts_times);
 }