Add an assertion when updating conversations; update cleanData

ts/util/assert.ts

@@ -0,0 +1,21 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { getEnvironment, Environment } from '../environment';
+import * as log from '../logging/log';
+
+/**
+ * In production, logs an error and continues. In all other environments, throws an error.
+ */
+export function assert(condition: unknown, message: string): asserts condition {
+  if (!condition) {
+    const err = new Error(message);
+    if (getEnvironment() !== Environment.Production) {
+      if (getEnvironment() === Environment.Development) {
+        debugger; // eslint-disable-line no-debugger
+      }
+      throw err;
+    }
+    log.error(err);
+  }
+}