Fix bugs in api_fuzzer

test/core/end2end/fuzzers/api_fuzzer.c

...pi_fuzzer_corpus/0242a9f4d4fafc96ee9ed762b610e3c68d6efdec

...pi_fuzzer_corpus/0cd9696699bd190463ecef91968624601b64cd8b

...pi_fuzzer_corpus/122b6fc72956541812dd653b726b073b77ca33be

...pi_fuzzer_corpus/315d27e12f2214a56fb9901dacff14852ff2ac0f

...pi_fuzzer_corpus/3f2429e3255ae36fecb57559b57d2b0cb88f5dd1

...pi_fuzzer_corpus/41bda7ff09175f821992adf4314a8ec3007ffe55

...pi_fuzzer_corpus/49d0085058d7fa81247f51b802c0f4206854b4dc

...pi_fuzzer_corpus/614dbc86b17270ef1d5ab705ecbe88c742815ce7

...pi_fuzzer_corpus/6cb17148d52be437332b6fd6f2fc8328bfb63fb0

...pi_fuzzer_corpus/6ea192b1d4c4577ca7511f8ce5027b31b2e0d75d

...pi_fuzzer_corpus/746477e7e8f093f87cb6924ab6476cda9689607d

...pi_fuzzer_corpus/7752153d87017b85112a49ea95aa25ca78d24431

...pi_fuzzer_corpus/7e75ea44aa7347c2f827beecb27e3bf5b1907b8a

...pi_fuzzer_corpus/95e73caecc0ab06beaa9b84125adcb2e6eee2eff

...pi_fuzzer_corpus/9e273a94bf3c60f1c7875874c81d0b9309428752

...pi_fuzzer_corpus/a65bda38b60ae084a5dcc3b616660aa338feef17

...pi_fuzzer_corpus/b39f27387a256019038cddb91f65651c01afb825

...pi_fuzzer_corpus/b6f721156f8dc6a353555929e459e61bab8b394a

...pi_fuzzer_corpus/bbb2429766a7c4ef9cb7110d567fd48cd6507dc5