fix(barcode-scanner): dispatch iOS cancel() cleanup to the main thread (#3393)

Signed-off-by: Alexis Zankowitch <a.zankowitch@reply.de>

.changes/barcode-scanner-ios-cancel-main-thread.md

@@ -0,0 +1,6 @@
+---
+"barcode-scanner": patch
+"barcode-scanner-js": patch
+---
+
+Fixed a crash on iOS when `cancel()` is invoked by running the cancel handler on the main thread.

plugins/barcode-scanner/ios/Sources/BarcodeScannerPlugin.swift

@@ -337,10 +337,11 @@ class BarcodeScannerPlugin: Plugin, AVCaptureMetadataOutputObjectsDelegate {
   }
 
   @objc private func cancel(_ invoke: Invoke) {
-    self.invoke?.reject("cancelled")
-
-    destroy()
-    invoke.resolve()
+    DispatchQueue.main.async { [self] in
+      self.invoke?.reject("cancelled")
+      self.destroy()
+      invoke.resolve()
+    }
   }
 }