Change hidden input id to avoid duplicated IDs

The TODOs dashboard already had a #project_id input and it was causing a spec to fail

app/assets/javascripts/search_autocomplete.js.coffee

@@ -17,7 +17,7 @@ class @SearchAutocomplete
     @locationBadgeEl = @$('.search-location-badge')
     @locationText = @$('.location-text')
     @searchInput = @$('.search-input')
-    @projectInputEl = @$('#project_id')
+    @projectInputEl = @$('#search_project_id')
     @groupInputEl = @$('#group_id')
     @searchCodeInputEl = @$('#search_code')
     @repositoryInputEl = @$('#repository_ref')

app/views/layouts/_search.html.haml

@@ -7,7 +7,7 @@
         = search_field_tag "search", nil, placeholder: 'Search', class: "search-input", spellcheck: false, tabindex: "1", autocomplete: 'off'
 
     = hidden_field_tag :group_id, @group.try(:id)
-    = hidden_field_tag :project_id, @project && @project.persisted? ? @project.id : ''
+    = hidden_field_tag :project_id, @project && @project.persisted? ? @project.id : '', id: 'search_project_id'
 
     - if @project && @project.persisted?
       - if current_controller?(:issues)