Fix crash when executing `Image.save_jpg_to_buffer` #29479

Job	Run time
📊 Static checks / Code style, file formatting, and docs	55s
🤖 Android / Template (target=template_release)	29m 32s
🍏 iOS / Template (target=template_release)	8m 48s
🐧 Linux / Editor w/ Mono (target=editor)	40m 18s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	4m 38s
🐧 Linux / Editor with doubles and GCC sanitizers (target=editor, tests=yes, dev_build=yes, scu_build=yes, precision=double, use_asan=yes, use_ubsan=yes, linker=gold)	44m 59s
🌐 Web / Template w/o threads (target=template_release, threads=no)	4m 39s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	34m 58s
🍎 macOS / Editor (target=editor, tests=yes)	27m 32s
🏁 Windows / Editor (target=editor, tests=yes)	47m 39s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	30m 53s
🍎 macOS / Template (target=template_release)	17m 38s
🐧 Linux / Template w/ Mono (target=template_release)	25m 48s
🏁 Windows / Template (target=template_release)	33m 44s
🐧 Linux / Minimal template (target=template_release, everything disabled)	13m 58s
🪲 Godot CPP / Build and test Godot CPP	7m 6s
	6h 13m 5s

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