vim7のChangeLogモードで\oするとエラーが出る

[changelog]/tmp/ChangeLog[euc-jp][unix]                             <1,1>    All
Error detected while processing function <SNR>53_new_changelog_entry:
line   12:
E121: Undefined variable: g:changelog_date_end_entry_search
E116: Invalid arguments for function search(g:changelog_date_end_entry_search, '
W') > 0
E15: Invalid expression: search(g:changelog_date_end_entry_search, 'W') > 0
line   19:
E121: Undefined variable: p
E116: Invalid arguments for function append
line   20:
E121: Undefined variable: p
E116: Invalid arguments for function cursor
Press ENTER or type command to continue

let g:changelog_date_end_entry_search = '^\s*$'