perf annotate browser: Be more robust when drawing jump arrows

This first happened with a gcc function, _cpp_lex_token, that has the
usual jumps:

 │1159e6c: ↓ jne    115aa32 <_cpp_lex_token@@Base+0xf92>

I.e. jumps to a label inside that function (_cpp_lex_token), and those
works, but also this kind:

 │1159e8b: ↓ jne    c469be <cpp_named_operator2name@@Base+0xa72>

I.e. jumps to another function, outside _cpp_lex_token, which are not
being correctly handled generating as a side effect references to
ab->offset[] entries that are set to NULL, so to make this code more
robust, check that here.

A proper fix for will be put in place, looking at the function name
right after the '<' token and probably treating this like a 'call'
instruction.

For now just don't draw the arrow.

Reported-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Ingo Molnar <mingo@kernel.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Link: https://lkml.kernel.org/n/tip-5tzvb875ep2sel03aeefgmud@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>