fixed compile error for msvc

7 jobs for featureMergePlugin in 37 minutes and 17 seconds
Status Job ID Name Coverage
  Test
passed clang-c++11-Qt5 #24069
Linux MultiThreads

00:10:54

passed cppcheck #24070
Linux MultiThreads

00:03:15

passed gcc-c++11-Qt5 #24068
Linux

00:23:05

passed Mac-Cpp11 #24074
Apple

00:37:16

passed VS2013-Qt-5.5.1-x64 #24073
VS2013 Qt551

00:15:51

passed VS2015-Qt-5.6.0-x32 #24072
VS2015 Qt56

00:20:51

passed VS2015-Qt-5.6.0-x64 #24071
VS2015 Qt56

00:17:44