refs #607 display a message in case user has not selected a zip file

plugins/CorePluginsAdmin/javascripts/pluginExtend.js

@@ -17,4 +17,14 @@ $(document).ready(function () {
         });
     });
 
+    $('#uploadPluginForm').submit(function (event) {
+
+        $zipFile = $('[name=pluginZip]');
+
+        if (!$zipFile.val()) {
+            event.preventDefault();
+            alert('Please select a ZIP file.');
+        }
+    });
+
 });
\ No newline at end of file

plugins/CorePluginsAdmin/templates/extend.twig

@@ -12,8 +12,10 @@
 
             <form enctype="multipart/form-data"
                   method="post"
+                  id="uploadPluginForm"
                   action="{{ linkTo({'action':'uploadPlugin', 'nonce': installNonce}) }}">
-                <input type="file" name="pluginZip"><br />
+                <input type="file" name="pluginZip">
+                <br />
                 <input class="startUpload" type="submit" value="Upload ZIP file">
             </form>
         </div>