listing: fix mailbox tree rendering

Indentation value was being interpreted mirrored (raw binary value in
parenthesis):

   0  testing_account (0)
   1   ┣━Archives     (0)
   2   ┃ ┣━2014       (1)
   3   ┃ ┃ ┗━10       (11)
   4   ┃ ┗━2015       (1)
   5     ┃ ┗━05       (10) <- invalid/mirrored
   6   ┣━Drafts       (0)

Should be:

   0  testing_account (0)
   1   ┣━Archives     (0)
   2   ┃ ┣━2014       (1)
   3   ┃ ┃ ┗━10       (11)
   4   ┃ ┗━2015       (1)
   5   ┃   ┗━05       (10)
   6   ┣━Drafts       (0)

src/components/mail/listing.rs

@@ -1652,15 +1652,15 @@ impl Listing {
             {
                 branches.clear();
                 branches.push_str(no_sibling_str);
-                let mut o = 1;
                 let leading_zeros = indentation.leading_zeros();
-                for _ in 0..(30_u32.saturating_sub(leading_zeros)) {
+                let mut o = 1_u32.wrapping_shl(31_u32.saturating_sub(leading_zeros));
+                for _ in 0..(32_u32.saturating_sub(leading_zeros)) {
                     if indentation & o > 0 {
                         branches.push_str(has_sibling_str);
                     } else {
                         branches.push_str(no_sibling_str);
                     }
-                    o <<= 1;
+                    o >>= 1;
                 }
                 if depth > 0 {
                     if has_sibling {

src/conf/accounts.rs

@@ -2310,6 +2310,6 @@ fn build_mailboxes_order(
             }
         };
 
-        rec(node, &mailbox_entries, 0, 1, false);
+        rec(node, &mailbox_entries, 0, 0, false);
     }
 }