fix early returns in iOS implementation of mobile scanner

@@ -37,24 +37,30 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin {
     
     init(barcodeHandler: BarcodeHandler, registry: FlutterTextureRegistry) {
         self.mobileScanner = MobileScanner(registry: registry, mobileScannerCallback: { barcodes, error, image in
-            if barcodes != nil {
+            if error != nil {
+                barcodeHandler.publishEvent(["name": "error", "data": error!.localizedDescription])
+                return
+            }
+            
+            if barcodes == nil {
+                return
+            }
+            
             let barcodesMap: [Any?] = barcodes!.compactMap { barcode in
-                    if (MobileScannerPlugin.scanWindow != nil) {
-                        if (MobileScannerPlugin.isBarcodeInScanWindow(barcode: barcode, imageSize: image.size)) {
+                if (MobileScannerPlugin.scanWindow == nil) {
                     return barcode.data
-                        } else {
-                            return nil
                 }
-                    } else {
+                
+                if (MobileScannerPlugin.isBarcodeInScanWindow(barcode: barcode, imageSize: image.size)) {
                     return barcode.data
                 }
+                
+                return nil
             }
+            
             if (!barcodesMap.isEmpty) {
                 barcodeHandler.publishEvent(["name": "barcode", "data": barcodesMap, "image": FlutterStandardTypedData(bytes: image.jpegData(compressionQuality: 0.8)!), "width": image.size.width, "height": image.size.height])
             }
-            } else if (error != nil){
-                barcodeHandler.publishEvent(["name": "error", "data": error!.localizedDescription])
-            }
         }, torchModeChangeCallback: { torchState in
             barcodeHandler.publishEvent(["name": "torchState", "data": torchState])
         }, zoomScaleChangeCallback: { zoomScale in
@@ -257,13 +263,15 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin {
                 DispatchQueue.main.async {
                     result(nil)
                 }
-            } else {
+                
+                return
+            }
+            
             let barcodesMap: [Any?] = barcodes!.compactMap { barcode in barcode.data }
             
             DispatchQueue.main.async {
                 result(["name": "barcode", "data": barcodesMap])
             }
-            }
         })
     }
 }