Check nullptr before calling the windows message hook for WM_ENTERSIZ… #98

Job	Run time
Create test plan	5s
level1 / Haiku	1m 47s
level2 / Windows (MSVC, x64)	5m 35s
level2 / Sony PlayStation 2	4m 44s
level2 / NetBSD	3m 57s
level2 / Sony PlayStation Vita (GLES w/ PVR_PSP2)	3m 4s
level2 / Ubuntu 20.04	5m 41s
level2 / RISC OS	1m 26s
level2 / Windows (MSVC, clang-cl x86)	6m 40s
level2 / Ubuntu 20.04 (Intel oneAPI)	7m 20s
level2 / Windows (msys2, mingw64)	8m 19s
level2 / tvOS (CMake & xcode)	2m 3s
level2 / PowerPC64	1m 52s
level2 / FreeBSD	2m 42s
level2 / Windows (MSVC, ARM64)	3m 54s
level2 / Android (CMake)	4m 7s
level2 / Windows (MSVC, x86)	5m 50s
level2 / LoongArch64	2m 56s
level2 / Windows (msys2, clang32)	7m 28s
level2 / Windows (msys2, ucrt64)	8m 38s
level2 / Android (Android.mk)	1m 11s
level2 / GDK (MSVC, x64)	2m 21s
level2 / Ubuntu 22.04	4m 44s
level2 / Sony PlayStation Portable	3m 39s
level2 / Ubuntu 20.04 (Intel Compiler)	6m 22s
level2 / Windows (MSVC, clang-cl x64)	4m 55s
level2 / MacOS (GNU prefix)	3m 33s
level2 / Windows (msys2, mingw32)	9m 3s
level2 / Android (Gradle)	2m 36s
level2 / Nintendo 3DS	1m 54s
level2 / Sony PlayStation Vita (GLES w/ pib)	3m 18s
level2 / Steam Linux Runtime (Sniper)	2m 50s
level2 / Windows (msys2, clang64)	5m 52s
level2 / iOS (CMake & xcode)	2m 18s
level2 / MacOS (Framework) (arm64)	2m 46s
level2 / Emscripten	8m 31s
level2 / MacOS (Framework) (x64)	6m 46s
level2 / Windows (MSVC, ARM)	4m 1s
level2 / PowerPC	1m 53s
level2 / Ubuntu 24.04 (ARM64)	4m 48s
level2 / Android (CMake, lean)	2m 51s
	2h 54m 20s

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