src/arm/Gex_tables.c: resolve possible null pointer dereference
src/arm/Gex_tables.c: resolve possible null pointer dereference

found by cppcheck

[src/arm/Gex_tables.c:159] -> [src/arm/Gex_tables.c:155]: (warning) Either the condition 'buf!=NULL' is redundant or there is pointer arithmetic with NULL pointer.

Upstreamed from dotnet/coreclr#26869

vtjnash/libunwind,vtjnash/libunwind,djwatson/libunwind,frida/libunwind,libunwind/libunwind,djwatson/libunwind,frida/libunwind,libunwind/libunwind,libunwind/libunwind,frida/libunwind,vtjnash/libunwind,djwatson/libunwind