When the help type is "html" and when a function name exists in different loaded libraries, the web browser is unable to display the package choice dialogue and display an error message.
"image" (packages graphics and gstat)
Error in httpd("/library/NULL/help/image", NULL, NULL, c(48, 6f, 73, 74, : replacement has length zero
This is now fixed; will commit after testing is done. (It was an error introduced in some unrelated changes. Unfortunately, our test suite doesn't include a robot testing all the interactive features of dynamic help.)