Don't display "git clone --bare <URL>" if no URL is available

Introduced in !1231

app/views/projects/imports/show.html.haml

@@ -4,7 +4,8 @@
     %h2
       %i.fa.fa-spinner.fa-spin
       Import in progress.
-    %p.monospace git clone --bare #{hidden_pass_url(@project.import_url)}
+    - if @project.import_url.present?
+      %p.monospace git clone --bare #{hidden_pass_url(@project.import_url)}
     %p Please wait while we import the repository for you. Refresh at will.
     :javascript
       new ProjectImport();