Fix the perfect storm of circumstances bug - #1608

Within a context that has no value, having two fairly specific two-way bindings before a conditional section (or probably anything else left unresolved due to the context ambiguity) would cause the mustache immediately after the second to be lost in the ether. All that was missing was a continue to avoid processing the same index twice in this type of scenario.

Hat tip to @anton-ryzhov for the excellent test-case distillery.
Style question: does it make more sense to `continue` here as in "the special case has triggered, move on now" or just change the following `if` to an `else if`?