Fix SyncEngine warning. (#404)

Author: mbrandonw

Sources/SQLiteData/CloudKit/SyncEngine.swift

@@ -2167,15 +2167,19 @@
     package var `private`: (any SyncEngineProtocol)? {
       guard let `private` = rawValue?.private
       else {
-        reportIssue("Private sync engine has not been set.")
+        if isRunning {
+          reportIssue("Private sync engine has not been set.")
+        }
         return nil
       }
       return `private`
     }
     package var `shared`: (any SyncEngineProtocol)? {
       guard let `shared` = rawValue?.shared
       else {
-        reportIssue("Shared sync engine has not been set.")
+        if isRunning {
+          reportIssue("Shared sync engine has not been set.")
+        }
         return nil
       }
       return `shared`

Tests/SQLiteDataTests/CloudKitTests/AppLifecycleTests.swift

@@ -51,6 +51,15 @@
         }
       }
 
+      @available(iOS 17, macOS 14, tvOS 17, watchOS 10, *)
+      @Test(.startImmediately(false))
+      func background_whileNotRunning() async throws {
+        defaultNotificationCenter.post(
+          name: UIApplication.willResignActiveNotification, object: nil)
+        try await Task.sleep(for: .seconds(1))
+        // NB: Not runtime warnings emitted.
+      }
+
       @available(iOS 17, macOS 14, tvOS 17, watchOS 10, *)
       @Test func sendSharedChanges() async throws {
         let externalZone = CKRecordZone(