fix: json error formatter when files are empty

Author: shyim

src/Command/ErrorFormatter/JsonErrorFormatter.php

@@ -60,6 +60,11 @@ public function formatErrors(AnalysisResult $analysisResult, Output $output): in
 			$errorsArray['errors'][] = $notFileSpecificError;
 		}
 
+		// When files empty format it as an empty object
+		if ($errorsArray['files'] === []) {
+			$errorsArray['files'] = new \stdClass();
+		}
+
 		$json = Json::encode($errorsArray, $this->pretty ? Json::PRETTY : 0);
 
 		$output->writeRaw($json);