Fix #300 in manner suggested by dansup

"you should be using url if preview_url returns public/no-preview.png or stick with url. The issue is a race condition and caching"

app/src/main/java/org/pixeldroid/app/posts/feeds/cachedFeeds/notifications/NotificationsFragment.kt

@@ -172,7 +172,7 @@ class NotificationsFragment : CachedFeedFragment<Notification>() {
             Glide.with(itemView).load(notification?.account?.anyAvatar()).circleCrop()
                 .into(avatar)
 
-            val previewUrl = notification?.status?.media_attachments?.getOrNull(0)?.preview_url
+            val previewUrl = notification?.status?.getPostPreviewURL()
             if (!previewUrl.isNullOrBlank()) {
                 Glide.with(itemView).load(previewUrl)
                     .placeholder(R.drawable.ic_picture_fallback).into(photoThumbnail)

app/src/main/java/org/pixeldroid/app/searchDiscover/SearchDiscoverFragment.kt

@@ -121,7 +121,7 @@ class SearchDiscoverFragment : BaseFragment() {
             } else {
                 holder.albumIcon.visibility = View.GONE
             }
-            ImageConverter.setSquareImageFromURL(holder.postView, post?.media_attachments?.firstOrNull()?.preview_url, holder.postPreview, post?.media_attachments?.firstOrNull()?.blurhash)
+            ImageConverter.setSquareImageFromURL(holder.postView, post?.getPostPreviewURL(), holder.postPreview, post?.media_attachments?.firstOrNull()?.blurhash)
             holder.postPreview.setOnClickListener {
                 val intent = Intent(holder.postView.context, PostActivity::class.java)
                 intent.putExtra(Status.POST_TAG, post)

app/src/main/java/org/pixeldroid/app/utils/api/objects/Attachment.kt

@@ -38,4 +38,8 @@ data class Attachment(
                 val aspect: Double?
         ) : Serializable
     }
+
+    val previewNoPlaceholder: String?
+        get() = if (preview_url?.contains(Regex("public/no-preview\\.(png|jpg|webp)")) == true) url else preview_url
+
 }

app/src/main/java/org/pixeldroid/app/utils/api/objects/Status.kt

@@ -65,7 +65,7 @@ open class Status(
 
     fun getPostUrl() : String? = media_attachments?.firstOrNull()?.url
     fun getProfilePicUrl() : String? = account?.anyAvatar()
-    fun getPostPreviewURL() : String? = media_attachments?.firstOrNull()?.preview_url
+    fun getPostPreviewURL() : String? = media_attachments?.firstOrNull()?.previewNoPlaceholder
 
 
     fun getNLikes(context: Context) : CharSequence {