check for null pointer before calling free

This commit was SVN r1826.

src/mca/ptl/tcp/src/ptl_tcp_module.c

@@ -164,7 +164,9 @@ int mca_ptl_tcp_module_close(void)
             mca_ptl_tcp_module.tcp_recv_frags.super.ompi_list_length);
     }
 
+    if(NULL != mca_ptl_tcp_module.tcp_if_include)
         free(mca_ptl_tcp_module.tcp_if_include);
+    if(NULL != mca_ptl_tcp_module.tcp_if_exclude)
        free(mca_ptl_tcp_module.tcp_if_exclude);
     if (NULL != mca_ptl_tcp_module.tcp_ptls)
         free(mca_ptl_tcp_module.tcp_ptls);