[vte] sixel: Add missing ifdef

[Christian Persch <chpe src gnome org>]

commit 35b0a8dc9776300bd33c8106e500436b6c11fccc
Author: Christian Persch <chpe src gnome org>
Date:   Sat Feb 13 21:31:08 2021 +0100

    sixel: Add missing ifdef

 src/parser-cat.cc | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/parser-cat.cc b/src/parser-cat.cc
index e9e5409d..5fade9db 100644
--- a/src/parser-cat.cc
+++ b/src/parser-cat.cc
@@ -753,6 +753,7 @@ public:
                         check_sgr(seq);
                         break;
 
+#ifdef WITH_SIXEL
                 case VTE_CMD_DECSIXEL:
                         /* OR mode is a nonstandard NetBSD/x68k extension that is
                          * not supported in VTE.
@@ -766,6 +767,7 @@ public:
                         if (seq.collect1(3) != -1)
                                 warn("DECSIXEL ID extension not supported");
                         break;
+#endif /* WITH_SIXEL */
 
                 default:
                         if (cmd >= VTE_CMD_NOP_FIRST)