Clear pk context and other minor changes in *_free() procedures
diff --git a/library/dhm.c b/library/dhm.c
index 82cbb0c..a30d9b5 100644
--- a/library/dhm.c
+++ b/library/dhm.c
@@ -428,11 +428,16 @@
  */
 void mbedtls_dhm_free( mbedtls_dhm_context *ctx )
 {
-    mbedtls_mpi_free( &ctx->pX ); mbedtls_mpi_free( &ctx->Vf );
-    mbedtls_mpi_free( &ctx->Vi ); mbedtls_mpi_free( &ctx->RP );
-    mbedtls_mpi_free( &ctx->K  ); mbedtls_mpi_free( &ctx->GY );
-    mbedtls_mpi_free( &ctx->GX ); mbedtls_mpi_free( &ctx->X  );
-    mbedtls_mpi_free( &ctx->G  ); mbedtls_mpi_free( &ctx->P  );
+    mbedtls_mpi_free( &ctx->pX );
+    mbedtls_mpi_free( &ctx->Vf );
+    mbedtls_mpi_free( &ctx->Vi );
+    mbedtls_mpi_free( &ctx->RP );
+    mbedtls_mpi_free( &ctx->K  );
+    mbedtls_mpi_free( &ctx->GY );
+    mbedtls_mpi_free( &ctx->GX );
+    mbedtls_mpi_free( &ctx->X  );
+    mbedtls_mpi_free( &ctx->G  );
+    mbedtls_mpi_free( &ctx->P  );
 
     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_dhm_context ) );
 }
diff --git a/library/pem.c b/library/pem.c
index 6069a23..897c8a0 100644
--- a/library/pem.c
+++ b/library/pem.c
@@ -423,9 +423,11 @@
 
 void mbedtls_pem_free( mbedtls_pem_context *ctx )
 {
-    if( ctx->buf != NULL )
+    if ( ctx->buf != NULL )
+    {
         mbedtls_platform_zeroize( ctx->buf, ctx->buflen );
-    mbedtls_free( ctx->buf );
+        mbedtls_free( ctx->buf );
+    }
     mbedtls_free( ctx->info );
 
     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_pem_context ) );
diff --git a/library/pk.c b/library/pk.c
index f05b139..08e9b44 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -61,10 +61,11 @@
  */
 void mbedtls_pk_free( mbedtls_pk_context *ctx )
 {
-    if( ctx == NULL || ctx->pk_info == NULL )
+    if( ctx == NULL )
         return;
 
-    ctx->pk_info->ctx_free_func( ctx->pk_ctx );
+    if ( ctx->pk_info != NULL )
+        ctx->pk_info->ctx_free_func( ctx->pk_ctx );
 
     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_pk_context ) );
 }
diff --git a/library/rsa.c b/library/rsa.c
index 88c1cf1..642e83a 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -2168,14 +2168,20 @@
  */
 void mbedtls_rsa_free( mbedtls_rsa_context *ctx )
 {
-    mbedtls_mpi_free( &ctx->Vi ); mbedtls_mpi_free( &ctx->Vf );
-    mbedtls_mpi_free( &ctx->RN ); mbedtls_mpi_free( &ctx->D  );
-    mbedtls_mpi_free( &ctx->Q  ); mbedtls_mpi_free( &ctx->P  );
-    mbedtls_mpi_free( &ctx->E  ); mbedtls_mpi_free( &ctx->N  );
+    mbedtls_mpi_free( &ctx->Vi );
+    mbedtls_mpi_free( &ctx->Vf );
+    mbedtls_mpi_free( &ctx->RN );
+    mbedtls_mpi_free( &ctx->D  );
+    mbedtls_mpi_free( &ctx->Q  );
+    mbedtls_mpi_free( &ctx->P  );
+    mbedtls_mpi_free( &ctx->E  );
+    mbedtls_mpi_free( &ctx->N  );
 
 #if !defined(MBEDTLS_RSA_NO_CRT)
-    mbedtls_mpi_free( &ctx->RQ ); mbedtls_mpi_free( &ctx->RP );
-    mbedtls_mpi_free( &ctx->QP ); mbedtls_mpi_free( &ctx->DQ );
+    mbedtls_mpi_free( &ctx->RQ );
+    mbedtls_mpi_free( &ctx->RP );
+    mbedtls_mpi_free( &ctx->QP );
+    mbedtls_mpi_free( &ctx->DQ );
     mbedtls_mpi_free( &ctx->DP );
 #endif /* MBEDTLS_RSA_NO_CRT */