unicode text must be sliced correctly.

svn: r13089

src/gen/plug/docbackend/docbackend.py

@@ -278,6 +278,8 @@ class DocBackend(object):
                 is <b>text</b><i><b> here</b> not</i>
                overwrite this method if this complexity is not needed. 
         """
+        #unicode text must be sliced correctly
+        text = unicode(text)
         FIRST = 0
         LAST = 1
         tagspos = {}