base: Don't print LICENSE warning for non-recipe context

Now bitbake is executing anonymous python fragments in bitbake -e,
ensure we don't show the error in that context (where PN would be
unchanged from default).

(From OE-Core rev: 79240b3af32c7fa44751752e9e8f2ff832439643)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/base.bbclass

@@ -456,7 +456,7 @@ python () {
 
     pn = d.getVar('PN')
     license = d.getVar('LICENSE')
-    if license == "INVALID":
+    if license == "INVALID" and pn != "defaultpkgname":
         bb.fatal('This recipe does not have the LICENSE field set (%s)' % pn)
 
     if bb.data.inherits_class('license', d):