Avoid decompiling NOPs for 0 count case

If we try to decompile a dex that isn't quickened, attempting to
decompile NOPs will cause aborts.

Test: test-art-host
Change-Id: I820d7bd67d05a749c70346de214ba86b51286964
diff --git a/runtime/dex_to_dex_decompiler.cc b/runtime/dex_to_dex_decompiler.cc
index b82f4f7..3ae3a52 100644
--- a/runtime/dex_to_dex_decompiler.cc
+++ b/runtime/dex_to_dex_decompiler.cc
@@ -100,7 +100,11 @@
         break;
 
       case Instruction::NOP:
-        DecompileNop(inst);
+        if (quicken_info_number_of_indices_ > 0) {
+          // Only try to decompile NOP if there are more than 0 indices. The 0 index case happens
+          // for tests like 981.
+          DecompileNop(inst);
+        }
         break;
 
       case Instruction::IGET_QUICK: