bitbake: data: Be explicit in data_db check

The if statement current causes the size of parent to be calcuated which
is like a len() operation on a datastore. Since we're only interested
whether the value is none, checking explictly for this gives a
small performance gain.

(Bitbake rev: 43a245bde318545ea75ca4ce7894395c1cf9b32a)

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

bitbake/lib/bb/data.py

@@ -59,7 +59,7 @@ def init():
 def init_db(parent = None):
     """Return a new object representing the Bitbake data,
     optionally based on an existing object"""
-    if parent:
+    if parent is not None:
         return parent.createCopy()
     else:
         return _dict_type()