Recipe listing pages assume base branch is product branch

Testing a sourcepackage branch on dogfood gives the following error:

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(Error ID: OOPS-1626DF58)

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Traceback (most recent call last):

    * Module zope.publisher.publish, line 134, in publish
      result = publication.callObject(request, obj)
    * Module canonical.launchpad.webapp.publication, line 436, in callObject
      return mapply(ob, request.getPositionalArguments(), request)
    * Module zope.publisher.publish, line 109, in mapply
      return debug_call(obj, args)
      __traceback_info__: <security proxied zope.browserpage.metaconfigure.SimpleViewClass from /srv/launchpad.net/codelines/current/lib/lp/code/templates/sourcepackagerecipe-listing.pt instance at 0xd7a36ec>
    * Module zope.publisher.publish, line 115, in debug_call
      return obj(*args)
    * Module canonical.launchpad.webapp.publisher, line 279, in __call__
      return self.render()
    * Module canonical.launchpad.webapp.publisher, line 264, in render
      return self.template()
    * Module zope.app.pagetemplate.viewpagetemplatefile, line 83, in __call__
      return self.im_func(im_self, *args, **kw)
    * Module zope.app.pagetemplate.viewpagetemplatefile, line 51, in __call__
      sourceAnnotations=getattr(debug_flags, 'sourceAnnotations', 0),
    * Module zope.pagetemplate.pagetemplate, line 115, in pt_render
      strictinsert=0, sourceAnnotations=sourceAnnotations)()
    * Module zope.tal.talinterpreter, line 271, in __call__
      self.interpret(self.program)
    * Module zope.tal.talinterpreter, line 343, in interpret
      handlers[opcode](self, args)
    * Module zope.tal.talinterpreter, line 888, in do_useMacro
      self.interpret(macro)
    * Module zope.tal.talinterpreter, line 343, in interpret
      handlers[opcode](self, args)
    * Module zope.tal.talinterpreter, line 533, in do_optTag_tal
      self.do_optTag(stuff)
    * Module zope.tal.talinterpreter, line 518, in do_optTag
      return self.no_tag(start, program)
    * Module zope.tal.talinterpreter, line 513, in no_tag
      self.interpret(program)
    * Module zope.tal.talinterpreter, line 343, in interpret
      handlers[opcode](self, args)
    * Module zope.tal.talinterpreter, line 531, in do_optTag_tal
      self.no_tag(stuff[-2], stuff[-1])
    * Module zope.tal.talinterpreter, line 513, in no_tag
      self.interpret(program)
    * Module zope.tal.talinterpreter, line 343, in interpret
      handlers[opcode](self, args)
    * Module zope.tal.talinterpreter, line 946, in do_defineSlot
      self.interpret(slot)
    * Module zope.tal.talinterpreter, line 343, in interpret
      handlers[opcode](self, args)
    * Module zope.tal.talinterpreter, line 821, in do_loop_tal
      self.interpret(block)
    * Module zope.tal.talinterpreter, line 343, in interpret
      handlers[opcode](self, args)
    * Module zope.tal.talinterpreter, line 533, in do_optTag_tal
      self.do_optTag(stuff)
    * Module zope.tal.talinterpreter, line 518, in do_optTag
      return self.no_tag(start, program)
    * Module zope.tal.talinterpreter, line 513, in no_tag
      self.interpret(program)
    * Module zope.tal.talinterpreter, line 343, in interpret
      handlers[opcode](self, args)
    * Module zope.tal.talinterpreter, line 852, in do_condition
      self.interpret(block)
    * Module zope.tal.talinterpreter, line 343, in interpret
      handlers[opcode](self, args)
    * Module zope.tal.talinterpreter, line 531, in do_optTag_tal
      self.no_tag(stuff[-2], stuff[-1])
    * Module zope.tal.talinterpreter, line 513, in no_tag
      self.interpret(program)
    * Module zope.tal.talinterpreter, line 343, in interpret
      handlers[opcode](self, args)
    * Module zope.tal.talinterpreter, line 742, in do_insertStructure_tal
      structure = self.engine.evaluateStructure(expr)
    * Module zope.tales.tales, line 696, in evaluate
      return expression(self)
      /srv/launchpad.net/codelines/current/lib/lp/code/templates/sourcepackagerecipe-listing.pt
      Line 31, Column 14
      Expression: <PathExpr standard:u'recipe/base_branch/product/fmt:link'>
         - Names:
            {'args': (),
             'context': <Person at 0xdb9366c abentley (Aaron Bentley)>,
             'default': <object object at 0x401c75b8>,
             'loop': {},
             'nothing': None,
             'options': {},
             'repeat': {},
             'request': <canonical.launchpad.webapp.servers.CodeBrowserRequest instance URL=https://code.dogfood.launchpad.net/%7Eabentley/+recipes>,
             'template': <z3c.ptcompat.ViewPageTemplateFile object at 0xcbee4ec>,
             'view': <zope.browserpage.metaconfigure.SimpleViewClass from /srv/launchpad.net/codelines/current/lib/lp/code/templates/sourcepackagerecipe-listing.pt object at 0xd7a36ec>,
             'views': <zope.app.pagetemplate.viewpagetemplatefile.ViewMapper object at 0xd7e88ec>}
    * Module zope.tales.expressions, line 217, in __call__
      return self._eval(econtext)
    * Module zope.tales.expressions, line 194, in _eval
      ob = self._subexprs[-1](econtext)
    * Module zope.tales.expressions, line 124, in _eval
      ob = self._traverser(ob, element, econtext)
    * Module zope.pagetemplate.engine, line 68, in __call__
      request=request)
    * Module zope.traversing.adapters, line 138, in traversePathElement
      return traversable.traverse(nm, further_path)
      __traceback_info__: (<canonical.launchpad.webapp.tales.NoneFormatter object at 0xc43712c>, 'link')
    * Module canonical.launchpad.webapp.tales, line 425, in traverse
      raise TraversalError(name)

LocationError: 'link'<br />