Use Safe Navigation Operator &.

app/views/customers/_details.html.erb

@@ -13,12 +13,12 @@
     
     <tr>
       <th><%=t(:label_primary_phone)%></th>
-      <td><%= number_to_phone(customer.primary_phone.gsub(/[^\d]/, '').to_i, area_code: true) if customer.primary_phone %></td>
+      <td><%= number_to_phone(customer&.primary_phone&.gsub(/[^\d]/, '').to_i, area_code: true) %></td>
     </tr>
     
     <tr>
       <th><%=t(:label_mobile_phone)%></th>
-      <td><%= number_to_phone(customer.mobile_phone.gsub(/[^\d]/, '').to_i, area_code: true) if customer.mobile_phone %></td>
+      <td><%= number_to_phone(customer&.mobile_phone&.gsub(/[^\d]/, '').to_i, area_code: true) %></td>
     </tr>
     
      <tr>

app/views/qbo/_last_sync.html.erb

@@ -1 +1 @@
-<b><%=t(:label_last_sync)%>: </b> <%= Qbo.last_sync if Qbo.exists? %>
+<b><%=t(:label_last_sync)%>: </b> <%= Qbo.last_sync %>

app/views/qbo/_settings.html.erb

@@ -66,12 +66,12 @@ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLI
 
      <tr>
         <th><%=t(:label_oauth_expires)%></th>
-        <td><%= if Qbo.exists? then QboConnectionService.current!.oauth2_access_token_expires_at end %>
+        <td><%= QboConnectionService.current!&.oauth2_access_token_expires_at %>
       </tr>
       
       <tr>
         <th><%=t(:label_oauth2_refresh_token_expires_at)%></th>
-        <td><%= if Qbo.exists? then QboConnectionService.current!.oauth2_refresh_token_expires_at end %>
+        <td><%= QboConnectionService.current!&.oauth2_refresh_token_expires_at %>
      </tr>
 
   </tbody>

lib/redmine_qbo/hooks/users_show_hook_listener.rb

@@ -20,7 +20,7 @@ module RedmineQbo
         #Employee.update_all
     
         # Check to see if there is a quickbooks user attached to the issue
-        @selected = context[:user].employee.id if context[:user].employee
+        @selected = context[:user]&.employee&.id
 
         # Generate the drop down list of quickbooks contacts
         return "<p>#{context[:form].select :employee_id, Employee.all.pluck(:name, :id), selected: @selected, include_blank: true}</p>"