NoMethodError in Shelf#edit

Showing /app/app/views/shelf/edit.html.erb where line #137 raised:

undefined method `name' for nil:NilClass
Extracted source (around line #137):
135
136
137
138
139
140
              
<%=
entry.book.entries.collect { |e|
e.shelf.name
}.find_all { |shelfname|
shelf.name != shelfname && shelfname !~ /_deleted/
}.collect { |shelfname|

Rails.root: /app

Application Trace | Framework Trace | Full Trace

Request

Parameters:

{"shelfname"=>"らっか", "isbn"=>"4004000149"}

Response

Headers:

None