Import mbedtls-3.6.2

Imports Mbed TLS 3.6.2 from https://github.com/Mbed-TLS/mbedtls.git
tags mbedtls-3.6.2, v3.6.2

Files that are not needed are removed:

cd lib/libmbedtls
rm -rf mbedtls
cp -R path/to/mbedtls-3.6.2/mbedtls .
cd mbedtls
rm CMakeLists.txt DartConfiguration.tcl Makefile
rm .gitignore .travis.yml .pylintrc .globalrc .mypy.ini BRANCHES.md
rm include/.gitignore include/CMakeLists.txt library/.gitignore
rm library/CMakeLists.txt library/Makefile
rm -r cmake
rm -rf .git .github doxygen configs programs scripts tests visualc
rm -rf 3rdparty ChangeLog.d docs pkgconfig .gitmodules .readthedocs.yaml
rm library/mps_*
cd ..
git add mbedtls

This is a complete overwrite of previous code so earlier changes in the
previous branch import/mbedtls-3.6.0 will be added on top of this
commit.

Signed-off-by: Sungbae Yoo <sungbaey@nvidia.com>
diff --git a/lib/libmbedtls/mbedtls/library/pem.c b/lib/libmbedtls/mbedtls/library/pem.c
index 0fee5df..0207601 100644
--- a/lib/libmbedtls/mbedtls/library/pem.c
+++ b/lib/libmbedtls/mbedtls/library/pem.c
@@ -481,6 +481,10 @@
 
 void mbedtls_pem_free(mbedtls_pem_context *ctx)
 {
+    if (ctx == NULL) {
+        return;
+    }
+
     if (ctx->buf != NULL) {
         mbedtls_zeroize_and_free(ctx->buf, ctx->buflen);
     }