Fix project find url so branch ref is not nil

Also adds autocomplete="off" to find input.

app/views/layouts/header/_default.html.haml

@@ -37,6 +37,10 @@
       %h1.title= title
 
 = render 'shared/outdated_browser'
-- if @project
+-if @project && !@project.empty_repo? && @ref
   :javascript
-    var findFileURL = '#{namespace_project_find_file_path(@project.namespace, @project, @ref || @project.repository.root_ref)}';
+    var findFileURL = '#{namespace_project_find_file_path(@project.namespace, @project, @ref)}';
+
+-elsif @project && !@project.empty_repo?
+  :javascript
+    var findFileURL = '#{namespace_project_find_file_path(@project.namespace, @project, @project.repository.root_ref)}';

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

@@ -10,7 +10,7 @@
         = link_to namespace_project_tree_path(@project.namespace, @project, @ref) do
           = @project.path
       %li.file-finder
-        %input#file_find.form-control.file-finder-input{type: "text", placeholder: 'Find by path'}
+        %input#file_find.form-control.file-finder-input{type: "text", placeholder: 'Find by path', autocomplete: 'off'}
 
   %div.tree-content-holder
     .table-holder