bgpd/eigrpd: fix crashes found by the CLI fuzzer

bgpd/eigrpd: fix crashes found by the CLI fuzzer

Fixes the following crashes:
* bgpd aborted: vtysh  -c "show ip bgp l2vpn evpn all 1.1.1.1 json"
* bgpd aborted: vtysh  -c "show ip bgp l2vpn evpn all 1.1.1.1"
* bgpd aborted: vtysh  -c "show ip bgp l2vpn evpn all 1.1.1.1/32 json"
* bgpd aborted: vtysh  -c "show ip bgp l2vpn evpn all 1.1.1.1/32"
* bgpd aborted: vtysh  -c "show bgp l2vpn evpn all 1.1.1.1 json"
* bgpd aborted: vtysh  -c "show bgp l2vpn evpn all 1.1.1.1"
* bgpd aborted: vtysh  -c "show bgp l2vpn evpn all 1.1.1.1/32 json"
* bgpd aborted: vtysh  -c "show bgp l2vpn evpn all 1.1.1.1/32"
* bgpd aborted: vtysh  -c "show bgp ipv4 vpn rd 1:1 1.1.1.1/32 json"
* bgpd aborted: vtysh  -c "show bgp ipv4 vpn rd 1:1 1.1.1.1/32"
* bgpd aborted: vtysh  -c "show bgp ipv4 vpn rd 1:1 2001:db8::1/128 json"
* bgpd aborted: vtysh  -c "show bgp ipv4 vpn rd 1:1 2001:db8::1/128"
* bgpd aborted: vtysh  -c "show bgp ipv6 vpn rd 1:1 1.1.1.1/32 json"
* bgpd aborted: vtysh  -c "show bgp ipv6 vpn rd 1:1 1.1.1.1/32"
* bgpd aborted: vtysh  -c "show bgp ipv6 vpn rd 1:1 2001:db8::1/128 json"
* bgpd aborted: vtysh  -c "show bgp ipv6 vpn rd 1:1 2001:db8::1/128"
* bgpd aborted: vtysh  -c "show vnc responses 1.1.1.1/32"
* bgpd aborted: vtysh  -c "show vnc responses 2001:db8::1/128"
* bgpd aborted: vtysh  -c "show vnc responses 11:11:11:11:11:11"
* bgpd aborted: vtysh  -c "show vnc responses"
* eigrpd aborted: vtysh -c "configure terminal" -c "no router eigrp 65535"

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>