foo.diff

diff --git a/src/hooks/useCategorizeFilters.ts b/src/hooks/useCategorizeFilters.ts
index 31d9740..8011ebe 100644
--- a/src/hooks/useCategorizeFilters.ts
+++ b/src/hooks/useCategorizeFilters.ts
@@ -60,10 +60,10 @@ export function useCategorizeFilters(
     const allReportIds = getIds(allReports);
 
     // 1. Compute deltas
-    const changedFilterIds = difference(allFilterIds, oldData.filterIds);
-    const removedFilterIds = difference(oldData.filterIds, allFilterIds);
-    const changedReportIds = difference(allReportIds, oldData.reportIds);
-    const removedReportIds = difference(oldData.reportIds, allReportIds);
+    const changedFilterIds = difference(allFilterIds, oldData?.filterIds);
+    const removedFilterIds = difference(oldData?.filterIds, allFilterIds);
+    const changedReportIds = difference(allReportIds, oldData?.reportIds);
+    const removedReportIds = difference(oldData?.reportIds, allReportIds);
 
     const hadAnyChanges =
       changedFilterIds.length ||
@@ -78,7 +78,7 @@ export function useCategorizeFilters(
     const allReportsById = makeDBDictionary(allReports);
 
     // 2a. Remove old hits by filters.
-    const filterHitIds = { ...oldData.filterHits };
+    const filterHitIds = { ...oldData?.filterHits };
     for (const filterId of removedFilterIds) {
       delete filterHitIds[filterId];
     }
@@ -141,7 +141,14 @@ export function useCategorizeFilters(
     console.log(
       `[categorization] ${duration}s - ${changedReportIds.length} new crashes, ${changedFilterIds.length}/${removedFilterIds.length} new/removed filters`
     );
-  }, [allFilters, allReports, filterHits, filterFilter, reportsLoading, filtersLoading]);
+  }, [
+    allFilters,
+    allReports,
+    filterHits,
+    filterFilter,
+    reportsLoading,
+    filtersLoading,
+  ]);
 
   const getFilterHitCount = useCallback(
     (filterId: number) => filterHits?.[filterId]?.length || 0,