title: How to fix: Exception evaluating SpringEL expression
body: <p>I am trying to save an "employee" model without assigning any "phone" model to it (oneToOne relationship). I have a form, in which i create the employee by adding: firstName, lastName and then a dropdown list from where i can select a phone to assign it. Whenever i do not select anything, the index.html page throws: Exception evaluating SpringEL expression: "employee.phone.getBrand() +' '+ employee.phone.getModel()" (template: "index" - line 31, col 17)</p>
  
  <pre><code>&lt;div align="center"&gt;
  &lt;table &gt;
      &lt;thead&gt;
      &lt;tr&gt;
          &lt;th&gt;Id Employee&lt;/th&gt;
          &lt;th&gt;Last Name&lt;/th&gt;
          &lt;th&gt;First Name&lt;/th&gt;
          &lt;th&gt;Phone&lt;/th&gt;
          &lt;th&gt;Manage&lt;/th&gt;
      &lt;/tr&gt;
      &lt;/thead&gt;
      &lt;tbody&gt;
      &lt;tr th:each="employee: ${employeeList} "&gt;
          &lt;td th:text="${employee.id}"&gt;Id&lt;/td&gt;
          &lt;td th:text="${employee.lastName}"&gt;Last Name&lt;/td&gt;
          &lt;td th:text="${employee.firstName}"&gt;First Name&lt;/td&gt;
          &lt;td th:text="${employee.phone.getBrand() +' '+ employee.phone.getModel()} "&gt;Brand&lt;/td&gt;
          &lt;td&gt;
              &lt;a th:href="@{'employee/edit/' + ${employee.id}}"&gt;&lt;button class="btnEdit"&gt;&lt;i class="fa fa-edit"&gt;&lt;/i&gt;&lt;/button&gt;&lt;/a&gt;
              &amp;nbsp &amp;nbsp
              &lt;a th:href="@{'employee/delete/' + ${employee.id}}"&gt;&lt;button class="btnDelete"&gt;&lt;i class="fa fa-edit"&gt;&lt;/i&gt;&lt;/button&gt;&lt;/a&gt;
          &lt;/td&gt;
      &lt;/tr&gt;
      &lt;/tbody&gt;
  &lt;/table&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>I mention that the object can be found in DB and the phone_id is null. I want to add some employees with a phone and some without any phone.
  The output should be: 
  Doe John noPhone -> nothing selected from dropdown list.
  Doe Jane iPhone 10s - > phone selected.</p>
  
  <p>Do you have any suggestions ?</p>