[FIX] l10n_be_inovice_bba: Missing field in supplier invoices

reference_type was already present in the customer invoice but not in the
supplier invoice

Closes #25732

addons/l10n_be_invoice_bba/views/account_invoice_view.xml

@@ -12,4 +12,15 @@
         </field>
       </field>
     </record>
+
+    <record id="supplier_invoice_bbacomm_form" model="ir.ui.view">
+        <field name="name">account.invoice.supplier.form</field>
+        <field name="model">account.invoice</field>
+        <field name="inherit_id" ref="account.invoice_supplier_form"/>
+        <field name="arch" type="xml">
+            <field name="reference" position="before">
+            <field name="reference_type" attrs="{'readonly':[('state','!=','draft')]}"/>
+            </field>
+        </field>
+    </record>
 </odoo>