Merged r68461 from 2.10 branch:

  Empty TALES path expressions are allowed in Zope 2.
  http://www.zope.org/Collectors/Zope/2118

lib/python/Products/PageTemplates/Expressions.py

@@ -99,6 +99,8 @@ def render(ob, ns):
 class ZopePathExpr(PathExpr):
 
     def __init__(self, name, expr, engine):
+        if not expr.strip():
+            expr = 'nothing'
         super(ZopePathExpr, self).__init__(name, expr, engine,
                                            boboAwareZopeTraverse)
 

lib/python/Products/PageTemplates/tests/testExpressions.py

@@ -86,6 +86,15 @@ class ExpressionTests(zope.component.testing.PlacelessSetup, unittest.TestCase):
         self.failUnless(isinstance(defer, DeferWrapper))
         self.failUnless(isinstance(lazy, LazyWrapper))
 
+    def test_empty_ZopePathExpr(self):
+        """Test empty path expressions.
+        """
+        ec = self.ec
+        self.assertEquals(ec.evaluate('path:'), None)
+        self.assertEquals(ec.evaluate('path:  '), None)
+        self.assertEquals(ec.evaluate(''), None)
+        self.assertEquals(ec.evaluate('  \n'), None)
+
 def test_suite():
     return unittest.makeSuite(ExpressionTests)