Fix leading zero added to UPC-A codes

AVFoundation adds a leading zero to UPC-A codes. We don't want an auto added zero
https://stackoverflow.com/questions/22767584/ios7-barcode-scanner-api-adds-a-zero-to-upca-barcode-format
https://developer.apple.com/library/content/technotes/tn2325/_index.html

Author: tapwork

Sources/BarcodeScannerController.swift

@@ -419,13 +419,18 @@ extension BarcodeScannerController: AVCaptureMetadataOutputObjectsDelegate {
 
     guard
       let metadataObj = metadataObjects[0] as? AVMetadataMachineReadableCodeObject,
-      let code = metadataObj.stringValue,
+      var code = metadataObj.stringValue,
       metadata.contains(metadataObj.type)
       else { return }
 
     if isOneTimeSearch {
       locked = true
     }
+    // See: https://stackoverflow.com/questions/22767584/ios7-barcode-scanner-api-adds-a-zero-to-upca-barcode-format
+    if metadataObj.type == AVMetadataObjectTypeEAN13Code && code.hasPrefix("0"){
+      let index = code.index(code.startIndex, offsetBy: 1)
+      code = code.substring(from: index)
+    }
 
     animateFlash(whenProcessing: isOneTimeSearch)
     codeDelegate?.barcodeScanner(self, didCaptureCode: code, type: metadataObj.type)