[umf] fix the last remaining coverity issue #1940

Job	Run time
Build - MacOS (macos-12)	7m 17s
Build - MacOS (macos-13)	6m 52s
Build - Windows (windows-2019, Debug)	10m 9s
Build - Windows (windows-2019, Release)	11m 56s
Build - Windows (windows-2022, Debug)	11m 41s
Build - Windows (windows-2022, Release)	13m 47s
Build - Ubuntu (ubuntu-20.04, Debug, gcc, g++, -DVAL_USE_LIBBACKTRACE_BACKTRACE=OFF)	9m 52s
Build - Ubuntu (ubuntu-20.04, Release, gcc, g++, -DVAL_USE_LIBBACKTRACE_BACKTRACE=OFF)	14m 14s
Build - Ubuntu (ubuntu-22.04, Debug, gcc, g++, -DVAL_USE_LIBBACKTRACE_BACKTRACE=OFF)	12m 15s
Build - Ubuntu (ubuntu-22.04, Release, gcc, g++, -DVAL_USE_LIBBACKTRACE_BACKTRACE=OFF)	11m 39s
Build - Ubuntu (ubuntu-22.04, Release, clang, clang++, -DVAL_USE_LIBBACKTRACE_BACKTRACE=OFF)	12m 9s
Build - Ubuntu (ubuntu-22.04, Release, gcc, g++, -DVAL_USE_LIBBACKTRACE_BACKTRACE=ON)	12m 27s
Build - Ubuntu (ubuntu-22.04, Release, clang, clang++, -DVAL_USE_LIBBACKTRACE_BACKTRACE=ON)	16m 22s
Build - Ubuntu (ubuntu-20.04, Release, gcc-7, g++-7)	13m 31s
	2h 44m 11s

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