Fix duplicate experiment row after first experiment creation (#3174)

Author: zackcl

packages/frontend/projects/upgrade/src/app/core/experiments/store/experiments.reducer.ts

@@ -94,9 +94,9 @@ const reducer = createReducer(
   on(experimentsAction.actionUpsertExperiment, experimentsAction.actionGetExperimentById, (state) => ({
     ...state,
     isLoadingExperiment: true,
-    // if we don't have a totalExperiments count yet (no paginated call with > 1 has occured yet),
-    // set it to 1 because we are loading at least one experiment so that nav to root page will not show empty template
-    totalExperiments: state.totalExperiments ? state.totalExperiments : 1,
+    // If the total count is unknown, assume at least one experiment is loading so the root page skips the empty state.
+    // Preserve 0 because it means the backend already confirmed an empty list.
+    totalExperiments: state.totalExperiments ?? 1,
   })),
   on(experimentsAction.actionGetExperimentByIdSuccess, (state, { experiment }) => {
     // Upsert experiment: update if exists, add if not (for direct navigation)