Add process for when the createdAt is null.

app/src/main/java/com/keylesspalace/tusky/adapter/NotificationsAdapter.java

@@ -388,8 +388,10 @@ public class NotificationsAdapter extends RecyclerView.Adapter {
                         sdf = new SimpleDateFormat("HH:mm:ss", Locale.getDefault());
                     }
                     time = sdf.format(createdAt);
-                    timestampInfo.setText(time);
+                } else {
+                    time = "??:??:??";
                 }
+                timestampInfo.setText(time);
             } else {
                 // This is the visible timestampInfo.
                 String readout;

app/src/main/java/com/keylesspalace/tusky/adapter/StatusBaseViewHolder.java

@@ -142,8 +142,10 @@ abstract class StatusBaseViewHolder extends RecyclerView.ViewHolder {
                     sdf = new SimpleDateFormat("HH:mm:ss", Locale.getDefault());
                 }
                 time = sdf.format(createdAt);
-                timestampInfo.setText(time);
+            } else {
+                time = "??:??:??";
             }
+            timestampInfo.setText(time);
         } else {
             // This is the visible timestampInfo.
             String readout;