bitbake/parse: Correctly handle multiline comments including whitespace

bitbake/parse: Correctly handle multiline comments including whitespace

[Richard Purdie]

If metadata contains:

"""

FOO = "bar"
"""

The variable FOO should get set to "bar" but doesn't due to the empty lines
be swallowed by the parser and FOO becomming part of the multiline comment.
This patch corrects that behaviour so FOO is set as expected.

[YOCTO #1377]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
---
diff --git a/bitbake/lib/bb/parse/parse_py/BBHandler.py b/bitbake/lib/bb/parse/parse_py/BBHandler.py
index 402cd07..c59b468 100644
--- a/bitbake/lib/bb/parse/parse_py/BBHandler.py
+++ b/bitbake/lib/bb/parse/parse_py/BBHandler.py
@@ -194,21 +194,21 @@ def feeder(lineno, s, fn, root, statements):
                 return
 
 
-    # Skip empty lines
-    if s == '':
-        return          
-
-    if s[0] == '#':
+    if s and s[0] == '#':
         if len(__residue__) != 0 and __residue__[0][0] != "#":
             bb.error("There is a comment on line %s of file %s (%s) which is in the middle of a multiline expression.\nBitbake used to ignore these but no longer does so, please fix your metadata as errors are likely as a result of this change." % (lineno, fn, s))
 
-    if s[-1] == '\\':
+    if s and s[-1] == '\\':
         __residue__.append(s[:-1])
         return
 
     s = "".join(__residue__) + s
     __residue__ = []
 
+    # Skip empty lines
+    if s == '':
+        return   
+
     # Skip comments
     if s[0] == '#':
         return