Protection against null proc.context in GPUWorkflow

Author: shahor02

GPU/Workflow/src/GPUWorkflowSpec.cxx

@@ -517,7 +517,7 @@ int32_t GPURecoWorkflowSpec::runMain(o2::framework::ProcessingContext* pc, GPUTr
     static bool first = true;
     if (first) {
       first = false;
-      if (pc->services().get<const o2::framework::DeviceSpec>().inputTimesliceId == 0) { // TPC ConfigurableCarams are somewhat special, need to construct by hand
+      if (pc && pc->services().get<const o2::framework::DeviceSpec>().inputTimesliceId == 0) { // TPC ConfigurableCarams are somewhat special, need to construct by hand
         o2::conf::ConfigurableParam::write(o2::base::NameConf::getConfigOutputFileName(pc->services().get<const o2::framework::DeviceSpec>().name, "rec_tpc"), "GPU_rec_tpc,GPU_rec,GPU_proc_param,GPU_proc,GPU_global,trackTuneParams");
       }
     }