Closes #693: fix ObjectiveC lexer throwing errors sometimes because bygroups() does not skip empty groups for callbacks.

1 files changed, 8 insertions, 6 deletions

diff --git a/pygments/lexer.py b/pygments/lexer.py
index 33427ae3..ecd11a5a 100644
--- a/pygments/lexer.py
+++ b/pygments/lexer.py
@@ -274,12 +274,14 @@ def bygroups(*args):
                 if data:
                     yield match.start(i + 1), action, data
             else:
-                if ctx:
-                    ctx.pos = match.start(i + 1)
-                for item in action(lexer, _PseudoMatch(match.start(i + 1),
-                                   match.group(i + 1)), ctx):
-                    if item:
-                        yield item
+                data = match.group(i + 1)
+                if data is not None:
+                    if ctx:
+                        ctx.pos = match.start(i + 1)
+                    for item in action(lexer, _PseudoMatch(match.start(i + 1),
+                                       data), ctx):
+                        if item:
+                            yield item
         if ctx:
             ctx.pos = match.end()
     return callback