[evolution] I#1061 - Mail preview can cause WebKit do 100% endless loop

[Milan Crha <mcrha src gnome org>]

commit 6ecd45610e52cfc19699814afe5f540608575b7c
Author: Milan Crha <mcrha redhat com>
Date:   Tue Aug 25 18:23:26 2020 +0200

    I#1061 - Mail preview can cause WebKit do 100% endless loop
    
    Closes https://gitlab.gnome.org/GNOME/evolution/-/issues/1061

 src/mail/e-mail-request.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/src/mail/e-mail-request.c b/src/mail/e-mail-request.c
index d4a19c2c3a..65038036c6 100644
--- a/src/mail/e-mail-request.c
+++ b/src/mail/e-mail-request.c
@@ -122,7 +122,8 @@ mail_request_process_mail_sync (EContentRequest *request,
 
        g_free (tmp);
 
-       if (!part_list && E_IS_MAIL_DISPLAY (requester)) {
+       if (!part_list && E_IS_MAIL_DISPLAY (requester) &&
+           e_mail_display_get_mode (E_MAIL_DISPLAY (requester)) == E_MAIL_FORMATTER_MODE_SOURCE) {
                part_list = e_mail_display_get_part_list (E_MAIL_DISPLAY (requester));
                if (part_list)
                        g_object_ref (part_list);