Prevent endless loop in PLY reader when unknown property types are read.

29 jobs for test_ply_reader in 66 minutes and 1 second (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #54393
VS2013
VS2013-32-bit-shared-apps

00:05:30

passed #54394
VS2013
VS2013-32-bit-shared-no-apps

00:05:07

passed #54397
VS2013
VS2013-32-bit-static-apps

00:05:36

passed #54398
VS2013
VS2013-32-bit-static-no-apps

00:05:15

passed #54391
VS2013
VS2013-64-bit-shared-apps

00:06:44

passed #54392
VS2013
VS2013-64-bit-shared-no-apps

00:05:17

passed #54395
VS2013
VS2013-64-bit-static-apps

00:06:24

passed #54396
VS2013
VS2013-64-bit-static-no-apps

00:05:59

passed #54385
VS2015
VS2015-32-bit-shared-apps

00:07:57

passed #54386
VS2015
VS2015-32-bit-shared-no-apps

00:06:12

passed #54389
VS2015
VS2015-32-bit-static-apps

00:07:08

passed #54390
VS2015
VS2015-32-bit-static-no-apps

00:06:21

passed #54383
VS2015
VS2015-64-bit-shared-apps

00:09:14

passed #54384
VS2015
VS2015-64-bit-shared-no-apps

00:07:23

passed #54387
VS2015
VS2015-64-bit-static-apps

00:09:24

passed #54388
VS2015
VS2015-64-bit-static-no-apps

00:08:42

passed #54380
VS2017
VS2017-32-bit-shared-no-apps

00:07:36

passed #54382
VS2017
VS2017-32-bit-static-no-apps

00:06:43

passed #54377
Qt5101 VS2017
VS2017-64-bit-shared-apps

00:07:59

passed #54379
VS2017
VS2017-64-bit-shared-no-apps

00:06:56

passed #54378
Qt5101 VS2017
VS2017-64-bit-static-apps

00:09:07

passed #54381
VS2017
VS2017-64-bit-static-no-apps

00:07:06

passed #54371
Linux
clang-c++11

00:39:44

passed #54373
Linux
clang-c++14

00:36:32

passed #54376
Linux
cppcheck

00:00:04

passed #54370
Linux
gcc-c++11

00:03:44

passed #54372
Linux
gcc-c++14

00:03:55

passed #54374
Apple
macos-c++11

00:23:32

passed #54375
Apple
macos-c++98

00:12:41