valgrind and coverity reported errors fixed. (ARMmbed#1838)

Coverity CID: 277994 fixed.

Author: deepakvenugopal

source/6LoWPAN/Thread/thread_extension.c

@@ -626,8 +626,11 @@ void thread_extension_address_registration(struct protocol_interface_info_entry
 void thread_extension_dua_address_generate(protocol_interface_info_entry_t *cur, uint8_t *domain_prefix, uint8_t domain_prefix_len)
 {
     if_address_entry_t *def_address = NULL;
-    addr_delete_matching(cur, NULL, 0, ADDR_SOURCE_THREAD_DOMAIN);
     uint8_t domain_address[16];
+    if (!thread_extension_version_check(thread_info(cur)->version)) {
+        return;
+    }
+    addr_delete_matching(cur, NULL, 0, ADDR_SOURCE_THREAD_DOMAIN);
     memcpy(domain_address, domain_prefix, 8);
     def_address = icmpv6_slaac_address_add(cur, domain_address, domain_prefix_len, 0xffffffff, 0xffffffff, true, SLAAC_IID_DEFAULT);
     if (def_address) {

source/6LoWPAN/Thread/thread_extension_bbr.c

@@ -873,6 +873,9 @@ static int thread_extension_bbr_dua_cb(int8_t service_id, uint8_t source_address
     }
     */
     protocol_interface_info_entry_t *cur = protocol_stack_interface_info_get_by_id(this->interface_id);
+    if (!cur) {
+        return -1;
+    }
     if (0 == thread_extension_primary_bbr_get(cur, bbr_rloc_addr, NULL, NULL, NULL) &&
             !addr_get_entry(cur,bbr_rloc_addr)) {
         // Primary pBBR present and I am not the pBBR