fix memory leak in DrawMeshT_impl

Patch by: Shaun Song <sxsong1207@qq.com>
26 jobs for memory_leak_drawmesh in 63 minutes and 27 seconds (queued for 2 minutes and 9 seconds)
Status Job ID Name Coverage
  Build
passed #94907
qt5113 Apple
Mac-Cpp11

00:28:34

passed #94905
Qt5101 VS2015
VS2015-Qt-5.10.1-x64

00:14:31

passed #94906
Qt5101 VS2017
VS2017-Qt-5.10.1

00:15:33

passed #94901
MultiThreads stretch Linux
clang-c++11-Qt5.11.2

00:10:45

passed #94902
MultiThreads stretch Linux
clang-c++11-Qt5.13.0

00:11:37

passed #94904
MultiThreads stretch Linux
cppcheck

00:02:14

passed #94903
MultiThreads stretch Linux
debug-clang-c++11-Qt5.13.0

00:17:50

passed #94900
stretch Linux
debug-gcc-c++11-Qt5.11.2

00:09:45

passed #94899
stretch Linux
debug-gcc-c++11-Qt5.13.0

00:10:33

passed #94896
stretch Linux
gcc-c++11-Qt5.11.2

00:05:25

passed #94897
stretch Linux
gcc-c++11-Qt5.11.2-nopython

00:06:45

passed #94894
stretch Linux
gcc-c++11-Qt5.12.2

00:05:52

passed #94895
stretch Linux
gcc-c++11-Qt5.12.2-nopython

00:04:51

passed #94898
stretch Linux
gcc-c++11-Qt5.13.0

00:07:14

 
  Test
passed #94918
qt5113 Apple
Test:Mac-Cpp11

00:00:41

passed #94916
Qt5101 VS2015
Test:VS2015-Qt-5.10.1-x64

00:01:21

passed #94917
Qt5101 VS2017
Test:VS2017-Qt-5.10.1

00:02:12

passed #94915
MultiThreads stretch Linux
debug-test-clang-c++11-Qt5.13.0

00:06:12

passed #94912
stretch Linux
debug-test-gcc-c++11-Qt5.11.2

00:06:57

passed #95160
Linux stretch
debug-test-gcc-c++11-Qt5.13.0

00:05:03

passed #94913
MultiThreads stretch Linux
test-clang-c++11-Qt5.11.2

00:01:33

passed #94914
MultiThreads stretch Linux
test-clang-c++11-Qt5.13.0

00:01:01

passed #94909
stretch Linux
test-gcc-c++11-Qt5.11.2

00:01:05

passed #94908
stretch Linux
test-gcc-c++11-Qt5.12.2

00:01:43

passed #94910
stretch Linux
test-gcc-c++11-Qt5.13.0

00:01:36

failed #94911
stretch Linux
debug-test-gcc-c++11-Qt5.13.0

00:02:30