entry-form: Clear YAML filename after loading

This way the test case can be re-loaded; otherwise it is
not recognized as a change and does not trigger the event.

src/current/scripts/entry-form.js

@@ -1515,11 +1515,18 @@ var client = ( function()
                 yamlconsole.style.display = '';
                 yamlconsole.textContent   = '';
 
+                if ( yamlbrowse.files.length === 0 )
+                {
+                    return;
+                }
+
                 runYamlTestCases(
                     Array.prototype.slice.call( yamlbrowse.files, 0 ),
                     createYamlRunner( yamlconsole )
                 );
 
+                yamlbrowse.value = '';
+
                 return false;
             } );