reverting change to make compute server associations ephemeral

- there are good reasons to want it to be ephemeral
- however, there are some subtle issues with user browser's having state
  they try to save after the project restarts, which leads to the new
  compute-servers.syncdb table closing.  This is a general tricky
  problem that needs to be robustly reproduced and solved before
  enabling ephemeral .compute-server.syncdb

src/packages/sync/editor/generic/sync-doc.ts

@@ -1867,6 +1867,11 @@ export class SyncDoc extends EventEmitter {
         continue;
       }
       const account_id = this.users[u[1]];
+      if (!account_id) {
+        // this happens for ephemeral table when project restarts and browser
+        // has data it is trying to send.
+        continue;
+      }
       const locs = this.cursors_table.get(k);
       if (locs == null && !this.cursor_map.has(account_id)) {
         // gone, and already gone.
@@ -2548,7 +2553,7 @@ export class SyncDoc extends EventEmitter {
     // TODO: handle doctype change here (?)
     this.last_snapshot = x.last_snapshot;
     this.snapshot_interval = x.snapshot_interval;
-    this.users = x.users;
+    this.users = x.users ?? [];
     // @ts-ignore
     this.project_id = x.project_id;
     // @ts-ignore

src/packages/util/compute/manager.ts

@@ -3,7 +3,7 @@ export const COMPUTER_SERVER_DB_NAME = ".compute-server.syncdb";
 export const SYNCDB_PARAMS = {
   path: COMPUTER_SERVER_DB_NAME,
   primary_keys: ["path"],
-  ephemeral: true,
+  ephemeral: false,
   cursors: true,
 };