Fix RAD nested riff precedence bug. #947

Job	Run time
unix-portable	1m 5s
unix	1m 13s
ARM-3DS	1m 11s
AArch64-Switch	1m 41s
ARM-NDS	33s
ARM-NDS-BlocksDS	50s
darwin-arm64	37s
darwin-x86_64	53s
MSYS2-MINGW32	2m 22s
MSYS2-MINGW64	2m 29s
PowerPC-Wii	1m 22s
unix-misc	2m 49s
AddressSanitizer	51s
Emscripten-HTML5	2m 19s
MemorySanitizer	1m 20s
PowerPC-WiiU	1m 30s
UndefinedBehaviorSanitizer	1m 48s
Vita	1m 41s
	26m 34s

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