Prevent crash

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

@@ -742,6 +742,7 @@ class Core {
                 HtmlHelper.getPreview(body),
                 parts.getWarnings(message.warning));
 
+        if (!TextUtils.isEmpty(body))
             fixAttachments(context, message.id, body);
     }
 
@@ -1708,6 +1709,8 @@ class Core {
                             parts.getWarnings(message.warning));
                     Log.i(folder.name + " downloaded message id=" + message.id +
                             " size=" + message.size + "/" + (body == null ? null : body.length()));
+
+                    if (!TextUtils.isEmpty(body))
                         fixAttachments(context, message.id, body);
                 }
             }