[PWGUD] fix ZDCtiming gapside selection (#18089)

Author: miedema-11

PWGUD/Tasks/flowCumulantsUpc.cxx

@@ -738,13 +738,13 @@ struct FlowCumulantsUpc {
       registry.fill(HIST("neutronClass"), 0, 0);
     }
     if (std::abs(timeZNA) <= cfgZdcTimeCut && std::abs(timeZNC) > cfgZdcTimeCut) {
-      neutronClass = 1;
-      registry.fill(HIST("neutronClass"), 0, 1);
-    }
-    if (std::abs(timeZNA) > cfgZdcTimeCut && std::abs(timeZNC) <= cfgZdcTimeCut) {
       neutronClass = 2;
       registry.fill(HIST("neutronClass"), 1, 0);
     }
+    if (std::abs(timeZNA) > cfgZdcTimeCut && std::abs(timeZNC) <= cfgZdcTimeCut) {
+      neutronClass = 1;
+      registry.fill(HIST("neutronClass"), 0, 1);
+    }
     if (std::abs(timeZNA) <= cfgZdcTimeCut && std::abs(timeZNC) <= cfgZdcTimeCut) {
       neutronClass = 3;
       registry.fill(HIST("neutronClass"), 1, 1);