v5: check imm > 0 instead of len_field > 0 before printing imm

Test: TH
Change-Id: I3c518fb67fcdd2f92da9d83f2c6089b6a88e6abd

disassembler.c

diff --git a/disassembler.c b/disassembler.c
index b638186..f544a40 100644
--- a/disassembler.c
+++ b/disassembler.c
@@ -135,7 +135,7 @@
             } else {
                 print_opcode("drop");
             }
-            if (len_field > 0) {
+            if (imm > 0) {
                 bprintf(" %d", imm);
             }
             break;