configure: always try at least one IMAP and SMTP server

Previously empty autoconfig resulted in no servers being tried and no
error displayed.

src/configure/mod.rs

@@ -217,28 +217,32 @@ async fn configure(ctx: &Context, param: &mut LoginParam) -> Result<()> {
 
     progress!(ctx, 500);
 
-    let servers = expand_param_vector(
+    let mut servers = param_autoconfig.unwrap_or_default();
-        param_autoconfig.unwrap_or_else(|| {
+    if !servers
-            vec![
+        .iter()
-                ServerParams {
+        .any(|server| server.protocol == Protocol::IMAP)
+    {
+        servers.push(ServerParams {
             protocol: Protocol::IMAP,
             hostname: param.imap.server.clone(),
             port: param.imap.port,
             socket: param.imap.security,
             username: param.imap.user.clone(),
-                },
+        })
-                ServerParams {
+    }
+    if !servers
+        .iter()
+        .any(|server| server.protocol == Protocol::SMTP)
+    {
+        servers.push(ServerParams {
             protocol: Protocol::SMTP,
             hostname: param.smtp.server.clone(),
             port: param.smtp.port,
             socket: param.smtp.security,
             username: param.smtp.user.clone(),
-                },
+        })
-            ]
+    }
-        }),
+    let servers = expand_param_vector(servers, &param.addr, &param_domain);
-        &param.addr,
-        &param_domain,
-    );
 
     progress!(ctx, 550);
 
@@ -560,7 +564,9 @@ async fn nicer_configuration_error(context: &Context, errors: Vec<ConfigurationE
     let first_err = if let Some(f) = errors.first() {
         f
     } else {
-        return "".to_string();
+        // This means configuration failed but no errors have been captured. This should never
+        // happen, but if it does, the user will see classic "Error: no error".
+        return "no error".to_string();
     };
 
     if errors