ffmpeg.php: fix mp4 logic for checking if audio exist

inc/lib/webm/ffmpeg.php

@@ -84,14 +84,29 @@ function is_valid_webm($ffprobe_out) {
 		}
 	} elseif ($extension === 'mp4' || stristr($ffprobe_out['format']['format_name'], 'mp4')) {
 		// If the video is not h264 or (there is audio but it's not aac).
-		if (($ffprobe_out['streams'][$videoidx]['codec_name'] != 'h264') || ((count($trackmap['audioat']) > 0) && ($ffprobe_out['streams'][$trackmap['audioat'][0]]['codec_name'] != 'aac'))) {
+		if ($ffprobe_out['streams'][$videoidx]['codec_name'] != 'h264') {
+			if (!isset($ffprobe_out['streams'][0]['codec_name'])) {
 				return [
 					'error' => [
 						'code' => 2,
-					'msg' => $config['error']['invalidwebm'] . ' [h264/aac check]'
+						'msg' => $config['error']['invalidwebm']
 					]
 				];
 			}
+
+			$video_codec = $ffprobe_out['streams'][0]['codec_name'];
+
+			$audio_codec = $ffprobe_out['streams'][1]['codec_name'] ?? null;
+
+			if ($video_codec !== 'h264' || ($audio_codec && $audio_codec !== 'aac')) {
+				return [
+					'error' => [
+						'code' => 2,
+						'msg' => $config['error']['invalidwebm']
+					]
+				];
+			}
+		}
 	} else {
 		return [
 			'error' => [