Fixes Wiki "Edit this section" does not extract SeText headings correctly in CommonMark Markdown (#40918).

git-svn-id: https://svn.redmine.org/redmine/trunk@24434 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/redmine/wiki_formatting/section_helper.rb

@@ -42,7 +42,7 @@ module Redmine
         i = 0
         l = 1
         inside_pre = false
-        @text.split(/(^(?:\S+\r?\n\r?(?:=+|-+)|#+ .+|(?:~~~|```).*)\s*$)/).each do |part|
+        @text.split(/(^(?:(?!\s*$|#).+\r?\n\r?(?:=+|-+)|#+ .+|(?:~~~|```).*)\s*$)/).each do |part|
           level = nil
           if part =~ /\A(~{3,}|`{3,})(\s*\S+)?\s*$/
             if !inside_pre