[web/views] Fix `has_editable_relation` predicate wrt inlined relations
Prevents the "modify" action from being shown when there is nothing to
edit.
import ConfigParser
try:
undo_actions = config.cfgfile_parser.get('MAIN', 'undo-support', False)
except ConfigParser.NoOptionError:
pass # this conf. file was probably already migrated
else:
config.global_set_option('undo-enabled', bool(undo_actions))