Clear init_msg/init_num whenever we clear the backing store.

This API needs to be improved but, for the time being, keep the
invariant reasonable.

Change-Id: If94d41e7e7936e44de5ecb36da45f89f80df7784
Reviewed-on: https://boringssl-review.googlesource.com/8984
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

ssl/ssl_lib.c

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 2608d87..71505eb 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -2824,6 +2824,8 @@
 
   BUF_MEM_free(ssl->init_buf);
   ssl->init_buf = NULL;
+  ssl->init_msg = NULL;
+  ssl->init_num = 0;
 
   /* The ssl->d1->mtu is simultaneously configuration (preserved across
    * clear) and connection-specific state (gets reset).