Remove close button if left bar button items are set

This fixes an issue with custom button actions not being called.
The close button can still be shown by adding 'close' to the button items.
If the left button items are not set, the close button will still be shown.

CordovaDemo/platforms/ios/CordovaDemo/Plugins/com.pspdfkit.cordovaplugin/PSPDFKitPlugin.m

@@ -866,6 +866,7 @@ - (void)setPageAnimatedForPSPDFViewControllerWithJSON:(NSNumber *)page
 
 - (void)setLeftBarButtonItemsForPSPDFViewControllerWithJSON:(NSArray *)items
 {
+    _pdfController.navigationItem.closeBarButtonItem = nil;
     _pdfController.navigationItem.leftBarButtonItems = [self barButtonItemsWithArray:items] ?: _pdfController.navigationItem.leftBarButtonItems;
 }