fix test?

Author: morganchen12

Firestore/Swift/Tests/Integration/AsyncAwaitIntegrationTests.swift

@@ -45,6 +45,7 @@ let emptyBundle = """
 
     func testRunTransactionDoesNotCrashOnNilSuccess() async throws {
       let document = collectionRef().document()
+      try await document.setData(["":""]) // ensure document exists
       let value = try await db.runTransaction { transact, error in
         transact.setData(["test": "test"], forDocument: document)
         return nil // should not crash