[balsa] mailbox: If priv->mindex is NULL, try again later

[Peter Bloomfield <peterb src gnome org>]

commit 5cd4f9b75e084f4b25509043c9eed540a044437a
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Mon Jan 13 15:47:04 2020 -0500

    mailbox: If priv->mindex is NULL, try again later

 libbalsa/mailbox.c | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/libbalsa/mailbox.c b/libbalsa/mailbox.c
index be43be74c..d7c62dd33 100644
--- a/libbalsa/mailbox.c
+++ b/libbalsa/mailbox.c
@@ -845,6 +845,12 @@ lbm_run_filters_on_reception_idle_cb(LibBalsaMailbox * mailbox)
 
     libbalsa_lock_mailbox(mailbox);
 
+    if (priv->mindex == NULL) {
+        libbalsa_unlock_mailbox(mailbox);
+        /* Try again later */
+        return TRUE;
+    }
+
     priv->run_filters_idle_id = 0;
 
     if (!priv->filters_loaded) {