Hide empty URL previews

Change-Id: I10a2f78e7efa96249adb7cd4849e54150a08001a

matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/media/PreviewUrlData.kt

@@ -48,4 +48,11 @@ data class PreviewUrlData(
         val description: String?,
         // Value of field "og:image"
         val mxcUrl: String?
-)
+) {
+    fun isPreviewable(): Boolean {
+        return siteName?.isNotEmpty() == true ||
+                title?.isNotEmpty() == true ||
+                description?.isNotEmpty() == true ||
+                mxcUrl?.isNotEmpty() == true
+    }
+}

vector/src/main/java/im/vector/app/features/home/room/detail/timeline/url/PreviewUrlRetriever.kt

@@ -65,6 +65,8 @@ class PreviewUrlRetriever(session: Session) {
                                 // Blocked after the request has been sent?
                                 if (urlToRetrieve in blockedUrl) {
                                     updateState(eventId, PreviewUrlUiState.NoUrl)
+                                } else if (!it.isPreviewable()) { // Nothing to show
+                                    updateState(eventId, PreviewUrlUiState.NoUrl)
                                 } else {
                                     updateState(eventId, PreviewUrlUiState.Data(eventId, urlToRetrieve, it))
                                 }