Update error handling and logging

javascript/gallery.js

@@ -577,8 +577,8 @@ async function thumbCacheCleanup() {
       const t1 = performance.now();
       log(`Thumbnail DB cleanup: kept=${thumbHashes.size} deleted=${delcount} time=${Math.floor(t1 - t0)}ms`);
     })
-    .catch(() => {
-      log("Thumbnail DB cleanup: Cleanup failed");
+    .catch((err) => {
+      error("Thumbnail DB cleanup: Cleanup failed.", err.message);
     })
     .finally(() => {
       idbIsCleaning = false;

javascript/indexdb.js

@@ -102,7 +102,7 @@ async function idbCount() {
 async function idbClean(keepSet) {
   if (!db) return null;
   if (!keepSet instanceof Set) {
-    console.error("IndexedDB cleaning function must be given a Set() of hashes to keep");
+    throw new TypeError("IndexedDB cleaning function must be given a Set() of hashes to keep");
   };
   return new Promise((resolve, reject) => {
     let counter = 0;