[IMP] web_editor: icon search empty screen

Before this commit:

There is not any message displayed when the search was performed on icons but
not received any results.

After this commit:

Now there is a no-content message so that users know that the search was
performed.

closes odoo/odoo#108029

Task: 2745855
X-original-commit: e7babea2b5ecaee550635adbaca435091f51a6cb
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>

addons/web_editor/static/src/components/media_dialog/icon_selector.xml

@@ -9,6 +9,10 @@
         </div>
         <div class="font-icons-icons">
             <t t-foreach="state.fonts" t-as="font" t-key="font.base">
+                <div t-if="!font.icons.length" class="o_nocontent_help">
+                    <p class="o_empty_folder_image">No pictograms found.</p>
+                    <p class="o_empty_folder_subtitle">Try searching with other keywords.</p>
+                </div>
                 <span t-foreach="font.icons" t-as="icon" t-key="icon.id"
                     t-att-title="icon.names[0]"
                     t-att-aria-label="icon.names[0]" role="img"