[geary] Always allow changing from address if account has multiple addresses

[Michael Gratton <mjog src gnome org>]

commit 77d8516e773edc6de793ab443f42a779bc1cbdc8
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Wed Dec 6 07:38:39 2017 -0600

    Always allow changing from address if account has multiple addresses
    
    https://bugzilla.gnome.org/show_bug.cgi?id=791230

 src/client/composer/composer-widget.vala |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/src/client/composer/composer-widget.vala b/src/client/composer/composer-widget.vala
index d2af409..a62bf0c 100644
--- a/src/client/composer/composer-widget.vala
+++ b/src/client/composer/composer-widget.vala
@@ -2053,9 +2053,10 @@ public class ComposerWidget : Gtk.EventBox {
             return false;
         }
 
-        // Don't show in inline, compact, or paned modes.
-        if (this.state == ComposerState.INLINE || this.state == ComposerState.INLINE_COMPACT ||
-            this.state == ComposerState.PANED)
+        // Don't show in inline, compact, or paned modes, unless the current
+        // account has multiple emails.
+        if ((this.state == ComposerState.INLINE || this.state == ComposerState.INLINE_COMPACT ||
+             this.state == ComposerState.PANED) && this.account.information.alternate_mailboxes == null)
             return false;
 
         // If there's only one account, show nothing. (From fields are hidden above.)