bug #695 Fixed #694 (sebastianlp)

This PR was merged into the master branch.

Discussion
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Fixed #694

In [Issue #694](https://github.com/javiereguiluz/EasyAdminBundle/issues/694) you can see that if use "es" as default locale you get the "form.label.empty_value" missing translation key.

Commits
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35b3576 Adds 'form.label.empty_value' key in messages.es.xlf dictionary

Resources/translations/messages.es.xlf

@@ -35,6 +35,10 @@
                 <source>action.list</source>
                 <target>Volver al listado</target>
             </trans-unit>
+            <trans-unit id="form.label.empty_value">
+                <source>form.label.empty_value</source>
+                <target>Ninguno</target>
+            </trans-unit>
         </body>
     </file>
 </xliff>