fix crash in polylinecollection, when no edge_scalars are present

7 jobs for polylinecollection in 64 minutes and 8 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed clang-c++11-Qt5 #17788
Linux MultiThreads

00:08:32

passed cppcheck #17789
Linux MultiThreads

00:38:49

passed gcc-c++11-Qt5 #17787
Linux

00:03:40

passed Mac-Cpp11 #17793
Apple

01:04:08

passed VS2013-Qt-5.5.1-x64 #17792
VS2013 Qt551

00:15:02

passed VS2015-Qt-5.6.0-x32 #17791
VS2015 Qt56

00:19:52

passed VS2015-Qt-5.6.0-x64 #17790
VS2015 Qt56

00:17:24