[FIX] web: displaying price on product stat button

Steps:
- Open Field Service
- Create a new task
- At first, the product stat button shows the price as 0.00
- Add task name and customer
- Save the task.
- Check product stat button

Issue:
- Now, after saving the task, the product stat button will not have the price
shown as it was displayed before.

Cause:
- The class o_field_empty is applied which has the property of display: none
and hence the price field is not displayed.

Fix:
- The o_field_empty class is applied at the wrong place, we need to apply the
o_field_empty only when o_stat_text is applied.

closes odoo/odoo#147926

Task: 3394985
X-original-commit: 9ea49b1e0be064ef4dd7dafe05aff4bd742ac135
Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>

addons/web/static/src/views/form/button_box/button_box.scss

@@ -67,15 +67,15 @@
 
             .o_stat_text {
                 @extend %-stat-button-text;
+                
+                .o_field_empty {
+                    display: none;
+                }
             }
 
             .o_stat_value {
                 @extend %-stat-button-value;
             }
-
-            .o_field_empty {
-                display: none;
-            }
         }
 
         &:not(:disabled) {