BUG/MINOR: debug: display (null) in place of "meth"

The array which contains names of types, miss the METH entry.

[wt: should be backported to 1.5 as well]
(cherry picked from commit 4c2479e1c455e2cc46c02cfc28ea2a185f9a7747)
diff --git a/src/sample.c b/src/sample.c
index 87c9f60..59c80b2 100644
--- a/src/sample.c
+++ b/src/sample.c
@@ -40,6 +40,7 @@
 	[SMP_T_IPV6] = "ipv6",
 	[SMP_T_STR]  = "str",
 	[SMP_T_BIN]  = "bin",
+	[SMP_T_METH] = "meth",
 };
 
 /* static sample used in sample_process() when <p> is NULL */