x11: add missing comma to fix compilation
diff --git a/src/mesa/drivers/x11/xm_dd.c b/src/mesa/drivers/x11/xm_dd.c
index 3a5d0ae..81d000b 100644
--- a/src/mesa/drivers/x11/xm_dd.c
+++ b/src/mesa/drivers/x11/xm_dd.c
@@ -588,7 +588,7 @@
                         "glDrawPixels(invalid PBO access)");
             return;
          }
-         buf = (GLubyte *) ctx->Driver.MapBufferRange(ctx, 0
+         buf = (GLubyte *) ctx->Driver.MapBufferRange(ctx, 0,
 						      unpack->BufferObj->Size,
 						      GL_MAP_READ_BIT,
 						      unpack->BufferObj);