Make article extractor report correct state on failed Mercury parses

Shared/Article Extractor/ArticleExtractor.swift

@@ -79,11 +79,12 @@ class ArticleExtractor {
 				decoder.dateDecodingStrategy = .iso8601
 				self.article = try decoder.decode(ExtractedArticle.self, from: data)
 				
-				self.state = .complete
                 DispatchQueue.main.async {
 					if self.article?.content == nil {
+						self.state = .failedToParse
 						self.delegate?.articleExtractionDidFail(with: URLError(.cannotDecodeContentData))
 					} else {
+						self.state = .complete
 						self.delegate?.articleExtractionDidComplete(extractedArticle: self.article!)
 					}
                 }