fix some signedness mismatches when indexing vectors with handle indexes

9 jobs for cmake-overhaul-3 in 4 minutes and 1 second (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #81318
VS2015
VS2015-32-bit

00:01:18

passed #81317
VS2015
VS2015-64-bit

00:01:32

passed #81316
VS2017
VS2017-32-bit

00:01:38

passed #81315
VS2015
VS2017-64-bit

00:01:28

passed #81312
Linux
clang-c++11

00:04:00

passed #81314
Linux
cppcheck

00:02:48

passed #81319
Linux
doc

00:00:23

passed #81311
Linux
gcc-c++11

00:03:08

passed #81313
Apple
macos-c++11

00:01:29