Added check for empty IV period of record before determining if flood stages should be fetched.

assets/src/scripts/monitoring-location/components/hydrograph/index.js

@@ -103,7 +103,7 @@ export const attachToNode = function(store,
 
     let fetchDataPromises = [fetchHydrographDataPromise];
     // Fetch waterwatch flood levels
-    if (config.GAGE_HEIGHT_PARAMETER_CODE in config.ivPeriodOfRecord) {
+    if (config.ivPeriodOfRecord && config.GAGE_HEIGHT_PARAMETER_CODE in config.ivPeriodOfRecord) {
         const fetchFloodLevelsPromise =  store.dispatch(floodDataActions.retrieveWaterwatchData(siteno));
         // If flood levels are to be shown then wait to render the hydrograph until those have been fetched.
         if (parameterCode === config.GAGE_HEIGHT_PARAMETER_CODE) {