fix missing Dispatch queue switch on MacOS

@@ -144,8 +144,10 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
                                 }
                                 }
                             }
                             }
                         } else {
                         } else {
+                            DispatchQueue.main.async {
                                 self?.sink?(FlutterError(code: "MobileScanner", message: error?.localizedDescription, details: nil))
                                 self?.sink?(FlutterError(code: "MobileScanner", message: error?.localizedDescription, details: nil))
                             }
                             }
+                        }
                     })
                     })
                     if(self?.symbologies.isEmpty == false){
                     if(self?.symbologies.isEmpty == false){
                         // add the symbologies the user wishes to support
                         // add the symbologies the user wishes to support
@@ -153,11 +155,13 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
                     }
                     }
                     try imageRequestHandler.perform([barcodeRequest])
                     try imageRequestHandler.perform([barcodeRequest])
                 } catch let e {
                 } catch let e {
+                    DispatchQueue.main.async {
                         self?.sink?(FlutterError(code: "MobileScanner", message: e.localizedDescription, details: nil))
                         self?.sink?(FlutterError(code: "MobileScanner", message: e.localizedDescription, details: nil))
                     }
                     }
                 }
                 }
             }
             }
         }
         }
+    }
     
     
     func checkPermission(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
     func checkPermission(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
         if #available(macOS 10.14, *) {
         if #available(macOS 10.14, *) {