BIO_s_mem() write: Skip early when input length is zero
When the input length is zero, just return zero early.  Otherwise,
there's a small chance that memory allocation is engaged, fails and
returns -1, which is a bit confusing when nothing should be written.
Fixes
@@ -216,6 +216,8 @@ static int mem_write(BIO *b, const char *in, int inl)
goto end;
}
BIO_clear_retry_flags(b);
+ if (inl == 0)
+ return 0;
blen = bbm->readp->length;
mem_buf_sync(b);
if (BUF_MEM_grow_clean(bbm->buf, blen + inl) == 0)
