tray: Don't call g_object_unref(NULL) #22

Job	Run time
Create test plan	8s
level1 / Haiku	1m 49s
level2 / Android (CMake, lean)	3m 1s
level2 / Sony PlayStation Vita (GLES w/ PVR_PSP2)	3m 12s
level2 / Ubuntu 20.04 (Intel Compiler)	4m 38s
level2 / Windows (MSVC, clang-cl x64)	5m 44s
level2 / Nintendo 3DS	2m 1s
level2 / MacOS (GNU prefix)	4m 26s
level2 / Windows (MSVC, x86)	5m 57s
level2 / Windows (MSVC, ARM64)	4m 39s
level2 / Windows (MSVC, clang-cl x86)	6m 18s
level2 / MacOS (Framework) (x64)	8m 55s
level2 / Sony PlayStation Vita (GLES w/ pib)	3m 8s
level2 / Android (Gradle)	2m 39s
level2 / RISC OS	1m 25s
level2 / Windows (msys2, mingw64)	9m 5s
level2 / Sony PlayStation Portable	3m 38s
level2 / tvOS (CMake & xcode)	2m 6s
level2 / Windows (MSVC, x64)	5m 52s
level2 / Windows (msys2, mingw32)	9m 53s
level2 / PowerPC	1m 49s
level2 / Android (CMake)	2m 58s
level2 / Android (Android.mk)	4m 39s
level2 / PowerPC64	1m 47s
level2 / Windows (msys2, clang64)	6m 54s
level2 / Sony PlayStation 2	4m 49s
level2 / iOS (CMake & xcode)	2m 14s
level2 / Ubuntu 20.04	4m 5s
level2 / Emscripten	9m 12s
level2 / Windows (msys2, ucrt64)	9m 10s
level2 / Ubuntu 20.04 (Intel oneAPI)	8m 1s
level2 / GDK (MSVC, x64)	3m 48s
level2 / Windows (msys2, clang32)	8m 22s
level2 / LoongArch64	3m 1s
level2 / FreeBSD	2m 37s
level2 / Steam Linux Runtime (Sniper)	2m 56s
level2 / Ubuntu 22.04	4m 19s
level2 / MacOS (Framework) (arm64)	2m 42s
level2 / Windows (MSVC, ARM)	4m 22s
level2 / NetBSD	3m 3s
	2h 59m 22s

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