fix MacOS leftover error codes

Author: navaronbracke

macos/mobile_scanner/Sources/mobile_scanner/MobileScannerPlugin.swift

@@ -465,20 +465,14 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
         let symbologies:[VNBarcodeSymbology] = argReader.toSymbology()
 
         guard let filePath: String = argReader.string(key: "filePath") else {
-            // TODO: fix error code
-            result(FlutterError(code: "MobileScanner",
-                                message: "No image found in analyzeImage!",
-                                details: nil))
+            result(nil)
             return
         }
 
         let fileUrl = URL(fileURLWithPath: filePath)
 
         guard let ciImage = CIImage(contentsOf: fileUrl) else {
-            // TODO: fix error code
-            result(FlutterError(code: "MobileScanner",
-                                message: "No image found in analyzeImage!",
-                                details: nil))
+            result(nil)
             return
         }
 
@@ -490,8 +484,9 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
 
                 if error != nil {
                     DispatchQueue.main.async {
-                        // TODO: fix error code
-                        result(FlutterError(code: "MobileScanner", message: error?.localizedDescription, details: nil))
+                        result(FlutterError(
+                            code: MobileScannerErrorCodes.BARCODE_ERROR,
+                            message: error?.localizedDescription, details: nil))
                     }
                     return
                 }
@@ -516,10 +511,11 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
             }
 
             try imageRequestHandler.perform([barcodeRequest])
-        } catch let e {
-            // TODO: fix error code
+        } catch let error {
             DispatchQueue.main.async {
-                result(FlutterError(code: "MobileScanner", message: e.localizedDescription, details: nil))
+                result(FlutterError(
+                    code: MobileScannerErrorCodes.BARCODE_ERROR,
+                    message: error.localizedDescription, details: nil))
             }
         }
     }