Glimpse: Use thumbnail cached image as full image preview

Change-Id: I87891cd8a2a687893e129cde28d5c5b3f43024dd
diff --git a/app/src/main/java/org/lineageos/glimpse/thumbnail/MediaViewerAdapter.kt b/app/src/main/java/org/lineageos/glimpse/thumbnail/MediaViewerAdapter.kt
index e462ccc..f88a866 100644
--- a/app/src/main/java/org/lineageos/glimpse/thumbnail/MediaViewerAdapter.kt
+++ b/app/src/main/java/org/lineageos/glimpse/thumbnail/MediaViewerAdapter.kt
@@ -95,6 +95,7 @@
             this.position = position
             imageView.load(media.externalContentUri) {
                 memoryCacheKey("full_${media.id}")
+                placeholderMemoryCacheKey("thumbnail_${media.id}")
             }
         }