feat(ui): add util to extract message from a tsafe AssertionError

Author: psychedelicious

invokeai/frontend/web/src/common/util/extractMessageFromAssertionError.ts

@@ -0,0 +1,6 @@
+import type { AssertionError } from 'tsafe';
+
+export function extractMessageFromAssertionError(error: AssertionError): string | null {
+  const match = error.message.match(/Wrong assertion encountered: "(.*)"/);
+  return match ? (match[1] ?? null) : null;
+}