avoid cppcheck warning

10 jobs for clean-cppcheck in 6 minutes and 30 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #75364
VS2015
VS2015-32-bit

00:01:11

passed #75363
VS2015
VS2015-64-bit

00:01:24

passed #75362
VS2017
VS2017-32-bit

00:01:16

passed #75361
VS2015
VS2017-64-bit

00:01:28

passed #75358
Linux
clang-c++11

00:03:41

passed #75360
Linux
cppcheck

00:00:34

passed #75365
Linux
doc

00:00:19

passed #75389
Linux
gcc-c++11

00:02:49

passed #75359
Apple
macos-c++11

00:01:37

failed #75357
Linux
gcc-c++11

00:00:00