Fix crash when generating blurhash image for AttachmentView that hasn't been laid out

It was passing a negative size into the blurhash decoder, which is invalid

Instead, cap the size at 32x32 (letting the image view scale it up when rendering)

Tusker/Views/Attachments/AttachmentView.swift

@@ -26,7 +26,6 @@ class AttachmentView: GIFImageView {
     
     var attachment: Attachment!
     var index: Int!
-    var expectedSize: CGSize!
     
     private var attachmentRequest: ImageCache.Request?
     private var source: Source?
@@ -37,13 +36,12 @@ class AttachmentView: GIFImageView {
     
     private var isGrayscale = false
 
-    init(attachment: Attachment, index: Int, expectedSize: CGSize) {
+    init(attachment: Attachment, index: Int) {
         super.init(image: nil)
         commonInit()
         
         self.attachment = attachment
         self.index = index
-        self.expectedSize = expectedSize
         loadAttachment()
     }
     
@@ -112,18 +110,8 @@ class AttachmentView: GIFImageView {
         if let hash = attachment.blurHash {
             AttachmentView.queue.async { [weak self] in
                 guard let self = self else { return }
-                let size: CGSize
-                if let meta = self.attachment.meta,
-                   let width = meta.width, let height = meta.height {
-                    size = CGSize(width: width, height: height)
-                } else if let orig = self.attachment.meta?.original,
-                          let width = orig.width, let height = orig.height {
-                    size = CGSize(width: width, height: height)
-                } else {
-                    size = self.expectedSize
-                }
                 
-                guard var preview = UIImage(blurHash: hash, size: size) else {
+                guard var preview = UIImage(blurHash: hash, size: self.blurHashSize()) else {
                     return
                 }
                 
@@ -153,6 +141,27 @@ class AttachmentView: GIFImageView {
         }
     }
     
+    private func blurHashSize() -> CGSize {
+        if let meta = self.attachment.meta {
+            let aspectRatio: CGFloat
+            if let width = meta.width, let height = meta.height {
+                aspectRatio = CGFloat(width) / CGFloat(height)
+            } else if let orig = meta.original,
+                      let width = orig.width, let height = orig.height {
+                aspectRatio = CGFloat(width) / CGFloat(height)
+            } else {
+                return CGSize(width: 32, height: 32)
+            }
+            if aspectRatio > 1 {
+                return CGSize(width: 32, height: 32 / aspectRatio)
+            } else {
+                return CGSize(width: 32 * aspectRatio, height: 32)
+            }
+        } else {
+            return CGSize(width: 32, height: 32)
+        }
+    }
+    
     func loadImage() {
         let attachmentURL = attachment.url
         attachmentRequest = ImageCache.attachments.get(attachmentURL) { [weak self] (data, _) in

Tusker/Views/Attachments/AttachmentsContainerView.swift

@@ -257,7 +257,7 @@ class AttachmentsContainerView: UIView {
         }
         let size = CGSize(width: width, height: height)
         
-        let attachmentView = AttachmentView(attachment: attachments[index], index: index, expectedSize: size)
+        let attachmentView = AttachmentView(attachment: attachments[index], index: index)
         attachmentView.delegate = delegate
         attachmentView.translatesAutoresizingMaskIntoConstraints = false
         attachmentView.accessibilityLabel = String(format: NSLocalizedString("Attachment %d", comment: "attachment at index accessiblity label"), index + 1)