fix an issue where thumbnail is not properly generated

SessionMessagingKit/Sending & Receiving/Attachments/ThumbnailService.swift

@@ -104,7 +104,7 @@ public class ThumbnailService {
         let thumbnailImage: UIImage
         
         if attachment.isImage || attachment.isAnimated {
-            thumbnailImage = try MediaUtils.thumbnail(forImageAtPath: originalFilePath, maxDimension: maxDimension)
+            thumbnailImage = try MediaUtils.thumbnail(forImageAtPath: originalFilePath, maxDimension: maxDimension, type: attachment.contentType)
         }
         else if attachment.isVideo {
             thumbnailImage = try MediaUtils.thumbnail(forVideoAtPath: originalFilePath, maxDimension: maxDimension)

SessionUtilitiesKit/Media/MediaUtils.swift

@@ -18,13 +18,13 @@ public enum MediaUtils {
     public static let maxStillImageDimensions: UInt = 8 * 1024
     public static let maxVideoDimensions: CGFloat = 3 * 1024
     
-    public static func thumbnail(forImageAtPath path: String, maxDimension: CGFloat) throws -> UIImage {
+    public static func thumbnail(forImageAtPath path: String, maxDimension: CGFloat, type: String) throws -> UIImage {
         SNLog("thumbnailing image: \(path)")
 
         guard FileManager.default.fileExists(atPath: path) else {
             throw MediaError.failure(description: "Media file missing.")
         }
-        guard Data.isValidImage(at: path) else {
+        guard Data.isValidImage(at: path, type: UTType(sessionMimeType: type)) else {
             throw MediaError.failure(description: "Invalid image.")
         }
         guard let originalImage = UIImage(contentsOfFile: path) else {