syz-manager: check new inputs from fuzzers
syz-manager: check new inputs from fuzzers

Fuzzer must not send broken programs, but we see such cases episodically.
Reason unknown. But at least prevent manager from crashing later.

google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller