[FIX] mail: correctly display unknown im status

Before this PR, the "unknown" im status was not properly
displayed. This commit ensures the question mark icon is displayed
when no im_status is available.

closes odoo/odoo#126958

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/static/src/core/common/im_status.xml

@@ -3,7 +3,7 @@
 
     <t t-name="mail.ImStatus" owl="1">
         <div class="o-mail-ImStatus d-flex justify-content-center flex-shrink-0 align-items-center rounded-circle o-bg-inherit" t-att-class="props.className" t-att-style="props.style">
-            <span t-if="props.persona.im_status" class="d-flex flex-column" name="icon">
+            <span class="d-flex flex-column" name="icon">
                 <i t-if="props.persona.im_status === 'online'" class="fa fa-circle text-success" title="Online" role="img" aria-label="User is online"/>
                 <i t-elif="props.persona.im_status === 'away'" class="fa fa-circle o-away" title="Idle" role="img" aria-label="User is idle"/>
                 <i t-elif="props.persona.im_status === 'offline'" class="fa fa-circle-o text-700" title="Offline" role="img" aria-label="User is offline"/>