[FIX] *: nocontent helper style for form view fields

*: hr_gamification, point_of_sale, web

Before this commit, no content helper in some form view fields were broken,
due to the style of the classname `.o_view_nocontent` that uses an absolute
position.

This is due to some templates that wrongly use this style for displaying a
help message, although this is only valid for views with no record.

This commit solves the issue by using another classname for those fields
with the nocontent helper, namely `.o_field_nocontent`.

addons/hr_gamification/views/hr_employee_views.xml

@@ -11,8 +11,8 @@
                 <page string="Received Badges" attrs="{'invisible': [('user_id', '=', False)]}">
                     <field name="has_badges" invisible="1"/>
                     <button string="Grant a Badge" type="action" name="%(action_reward_wizard)d"/> to reward this employee for a good action
-                    <div class="o_view_nocontent" attrs="{'invisible': [('has_badges', '=', True)]}">
-                        <p class="o_view_nocontent_smiling_face">
+                    <div class="o_field_nocontent" attrs="{'invisible': [('has_badges', '=', True)]}">
+                        <p>
                             Grant this employee his first badge
                         </p><p class="oe_grey">
                             Badges are rewards of good work. Give them to people you believe deserve it.

addons/point_of_sale/views/pos_session_view.xml

@@ -92,11 +92,11 @@
                                 <field name="cash_register_balance_end" nolabel="1" attrs="{'invisible' : [('state', '=', 'opening_control')]}" class="oe_bold oe_pos_total" widget="monetary" options="{'currency_field': 'currency_id'}"/>
                             </group>
                             <div class="oe_clear"/>
-                            <div attrs="{'invisible' : ['|', ('cash_journal_id', '=', False), ('state', '!=', 'opening_control')]}" class="o_view_nocontent" groups="point_of_sale.group_pos_manager">
-                                <p class="o_view_nocontent_smiling_face">
-                                You can define another list of available currencies on the
-                                <i>Cash Registers</i> tab of the <b><field name="cash_journal_id" class="oe_inline"/></b>
-                                payment method.
+                            <div attrs="{'invisible' : ['|', ('cash_journal_id', '=', False), ('state', '!=', 'opening_control')]}" class="o_field_nocontent" groups="point_of_sale.group_pos_manager">
+                                <p>
+                                    You can define another list of available currencies on the
+                                    <i>Cash Registers</i> tab of the <b><field name="cash_journal_id" class="oe_inline"/></b>
+                                    payment method.
                                 </p>
                             </div>
                         </div>

addons/web/static/src/less/views.less

@@ -40,10 +40,10 @@
 
 // No content helper
 .o_view_nocontent {
-    .o-position-absolute(20%, 0, 0, 0);        
+    .o-position-absolute(20%, 0, 0, 0);
     pointer-events: none;
     z-index: 1;
-    
+
     .o_nocontent_help {
         pointer-events: auto;
         max-width: 650px;