One fix and one enhancement to AI shield behavior #5647

Job	Run time
Windows (Debug, MSVC, Win32)	15m 12s
Mac (Release, clang, x86_64)	7m 15s
Mac (Debug, clang, arm64)	5m 10s
Mac (Debug, clang, x86_64)	5m 57s
Mac (Release, clang, arm64)	7m 0s
Windows (Debug, MSVC, x64)	15m 15s
Linux (Debug, clang-16)	14m 6s
Linux (Debug, gcc-9)	14m 51s
Windows (Release, MSVC, Win32)	18m 33s
Linux (Debug, gcc-13)	10m 41s
Linux (Release, clang-16)	19m 38s
Linux (Release, gcc-13)	14m 13s
Windows (Release, MSVC, x64)	20m 43s
Linux (Release, gcc-9)	19m 12s
Linux (Debug, gcc-13, -DFSO_BUILD_WITH_OPENGL=OFF -DFSO_BUILD_WITH_VULKAN=OFF)	10m 55s
Linux (Release, gcc-13, -DFSO_BUILD_WITH_OPENGL=OFF -DFSO_BUILD_WITH_VULKAN=OFF)	13m 56s
	3h 32m 37s

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