Improved compose/attachment error handling

app/src/main/java/eu/faircode/email/FragmentCompose.java

@@ -4427,7 +4427,7 @@ public class FragmentCompose extends FragmentBase {
             // Reset progress on failure
             Log.e(ex);
             db.attachment().setError(attachment.id, Log.formatThrowable(ex, false));
-            throw ex;
+            return null;
         }
 
         return attachment;
@@ -5425,7 +5425,7 @@ public class FragmentCompose extends FragmentBase {
 
                 if (last_attachments != null)
                     for (EntityAttachment attachment : last_attachments)
-                        if (!attachment.available && attachment.progress == null)
+                        if (!attachment.available && attachment.progress == null && attachment.error == null)
                             EntityOperation.queue(context, data.draft, EntityOperation.ATTACHMENT, attachment.id);
 
                 db.setTransactionSuccessful();