Enhance error handling to make syncing more resilient to network failures.

Frameworks/Account/Feedbin/FeedbinAPICaller.swift

@@ -428,6 +428,7 @@ final class FeedbinAPICaller: NSObject {
 				completion(.success((entries, pagingInfo.nextPage, lastPageNumber)))
 				
 			case .failure(let error):
+				self?.accountMetadata?.lastArticleFetch = nil
 				completion(.failure(error))
 			}
 			
@@ -444,7 +445,7 @@ final class FeedbinAPICaller: NSObject {
 		
 		let request = URLRequest(url: callURL, credentials: credentials)
 
-		transport.send(request: request, resultType: [FeedbinEntry].self) { result in
+		transport.send(request: request, resultType: [FeedbinEntry].self) { [weak self] result in
 			
 			switch result {
 			case .success(let (response, entries)):
@@ -453,6 +454,7 @@ final class FeedbinAPICaller: NSObject {
 				completion(.success((entries, pagingInfo.nextPage)))
 
 			case .failure(let error):
+				self?.accountMetadata?.lastArticleFetch = nil
 				completion(.failure(error))
 			}
 			

Frameworks/Account/Feedbin/FeedbinAccountDelegate.swift

@@ -164,6 +164,7 @@ final class FeedbinAccountDelegate: AccountDelegate {
 			case .failure(let error):
 				guard let self = self else { return }
 				os_log(.info, log: self.log, "Retrieving unread entries failed: %@.", error.localizedDescription)
+				group.leave()
 			}
 			
 		}
@@ -177,6 +178,7 @@ final class FeedbinAccountDelegate: AccountDelegate {
 			case .failure(let error):
 				guard let self = self else { return }
 				os_log(.info, log: self.log, "Retrieving starred entries failed: %@.", error.localizedDescription)
+				group.leave()
 			}
 			
 		}
@@ -1068,6 +1070,7 @@ private extension FeedbinAccountDelegate {
 			case .failure(let error):
 				guard let self = self else { return }
 				os_log(.error, log: self.log, "Refresh articles for additional pages failed: %@.", error.localizedDescription)
+				completion()
 			}
 			
 		}