don't emit an OM error message for every face that could not be added

Status Job ID Name Coverage
  Test
passed clang-c++11-Qt4 #4107
Linux MultiThreads

00:07:50

passed clang-c++11-Qt5 #4111
Linux MultiThreads

00:09:26

passed clang-c++98-Qt4 #4109
Linux MultiThreads

00:06:54

passed clang-c++98-Qt5 #4113
Linux MultiThreads

00:08:14

passed gcc-c++11-Qt4 #4106
Linux

00:05:36

passed gcc-c++11-Qt5 #4110
Linux

00:05:46

passed gcc-c++98-Qt4 #4108
Linux

00:03:34

passed gcc-c++98-Qt5 #4112
Linux

00:03:32