why is replace.mk complaining about gsed?

[John Marino <marino%netbsd.org@localhost>]

When I go to editors/emacs20 and type "bmake -V '${DEPENDS}'", I get
the following error message:

bmake: "../../mk/tools/../../mk/tools/replace.mk" line 171: 
Malformed conditional ((${_TOOLS_DEPMETHOD.gsed} == "BUILD_DEPENDS") &&  
defined(_TOOLS_DEPMETHOD.sed))

The code in question looks like this:

.if !empty(_USE_TOOLS:Mgsed)            # gsed > sed
.  if (${_TOOLS_DEPMETHOD.gsed} == "BUILD_DEPENDS") && \
      defined(_TOOLS_DEPMETHOD.sed)
_TOOLS_DEPMETHOD.gsed=          ${_TOOLS_DEPMETHOD.sed}
.  endif
.endif

The problem is _TOOLS_DEPMETHOD.gsed is an empty string.  Putting quotes
around "${_TOOLS_DEPMETHOD.gsed}" solves the problem.  I assume quotes are
missing intentionally from replace.mk.  So my question is: What's causing 
${_TOOLS_DEPMETHOD.gsed} to not be defined, and what's the proper fix?  Or
is this just a straight-up bug?  Another DragonFly user is seeing a very
similar message revolving around flex using 2010Q3 branch.

John