Fix nil import error?

Author: morganchen12

Firestore/Source/Public/FirebaseFirestore/FIRFirestore.h

@@ -143,7 +143,8 @@ NS_SWIFT_NAME(Firestore)
  *     block will run even if the client is offline, unless the process is killed.
  */
 - (void)runTransactionWithBlock:(id _Nullable (^)(FIRTransaction *, NSError **))updateBlock
-                     completion:(void (^)(id _Nullable result, NSError *_Nullable error))completion;
+                     completion:(void (^)(id _Nullable result, NSError *_Nullable error))completion
+                         __attribute__((swift_async_error(nonnull_error)));
 
 /**
  * Creates a write batch, used for performing multiple writes as a single

Firestore/Swift/Tests/Integration/AsyncAwaitIntegrationTests.swift

@@ -43,6 +43,16 @@ let emptyBundle = """
       XCTAssertTrue(snapshot.exists)
     }
 
+    func testRunTransactionDoesNotCrashOnNilSuccess() async throws {
+      let document = collectionRef().document()
+      let value = try await db.runTransaction({ transact, error in
+        transact.setData(["test": "test"], forDocument: document)
+        return nil // should not crash
+      })
+
+      XCTAssertNil(value, "value should be nil on success")
+    }
+
     func testLoadBundleFromData() async throws {
       let bundle = "\(emptyBundle.count)\(emptyBundle)"
       let bundleProgress = try await db.loadBundle(Data(bundle.utf8))