python/retrace: Cope with null constant buffers.

diff --git a/src/gallium/state_trackers/python/retrace/interpreter.py b/src/gallium/state_trackers/python/retrace/interpreter.py
index c3bc6bc..348f2e4 100755 (executable)
--- a/src/gallium/state_trackers/python/retrace/interpreter.py
+++ b/src/gallium/state_trackers/python/retrace/interpreter.py
@@ -459,7 +459,7 @@ class Context(Object):
         sys.stdout.flush()
 
     def set_constant_buffer(self, shader, index, buffer):
-        if buffer is not None:
+        if buffer is not None and buffer.buffer is not None:
             self.real.set_constant_buffer(shader, index, buffer.buffer)
 
             self.dump_constant_buffer(buffer.buffer)