Fixed code in vm_pop_hword DWORD -> DHWORD

Though practically this would work, as the storage for the half word is
not limited in any way, nevertheless it isn't syntactically right and
it's better to fix now.

vm/runtime.c

@@ -906,7 +906,7 @@ err_t vm_pop_hword(vm_t *vm, data_t *ret)
     vm_pop_byte(vm, &b);
     bytes[i] = b.as_byte;
   }
-  *ret = DWORD(convert_bytes_to_hword(bytes));
+  *ret = DHWORD(convert_bytes_to_hword(bytes));
   return ERR_OK;
 }