bitbake: ConfHandler.py: allow require or include without parameter

Writing .bbappends that only have an effect when some configuration
variable like DISTRO_FEATURES is changed becomes easier when allowing
"include" or "require" without a parameter. The same was already
allowed for "inherit".

Then one can write in a .bbappend:

  require ${@bb.utils.contains('DISTRO_FEATURES', 'foo', 'bar.inc', '', d)}

(Bitbake rev: 8b39c6361758b96fce50a53a6dba8008cd7e6433)

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/parse/parse_py/ConfHandler.py

@@ -81,6 +81,10 @@ def include(parentfn, fn, lineno, data, error_out):
     fn = data.expand(fn)
     parentfn = data.expand(parentfn)
 
+    if not fn:
+        # "include" or "require" without parameter is fine, just return.
+        return
+
     if not os.path.isabs(fn):
         dname = os.path.dirname(parentfn)
         bbpath = "%s:%s" % (dname, data.getVar("BBPATH"))