Set default country code to avoid crash

countryCode of NSLocale can be nil. App will crash:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[3]'
*** First throw call stack:
(
	0   CoreFoundation                      0x0000000106432495 __exceptionPreprocess + 165
	1   libobjc.A.dylib                     0x000000010368c99e objc_exception_throw + 43
	2   CoreFoundation                      0x00000001063fbdce -[__NSPlaceholderDictionary initWithObjects:forKeys:count:] + 382
	3   CoreFoundation                      0x000000010642723f +[NSDictionary dictionaryWithObjects:forKeys:count:] + 63
	4   APP iOS                             0x0000000100035389 -[TOLDeveloperAds fetchDeveloperMetadataWithSuccess:failure:] + 569
	5   APP iOS                             0x000000010003255e -[TOLDeveloperAds requestNextAdBanner] + 542
	6   APP iOS                             0x00000001000382b7 -[TOLDeveloperAds startAdRequests] + 231
	7   APP iOS                             0x000000010003fc57 -[LARSAdController startAdNetworkAdapterClass:] + 1463
	8   APP iOS                             0x000000010003f659 -[LARSAdController startAdNetworkAdapterClassAtIndex:] + 473
	9   APP iOS                             0x000000010003b129 -[LARSAdController addAdContainerToView:withParentViewController:] + 473


Steps to reproduce: set region format to Esperanto:
Settings > General > International > Region Format > Esperanto