fix: allow all traffic if acls field is omited from the policy

hscontrol/policy/v2/filter.go

@@ -21,7 +21,7 @@ func (pol *Policy) compileFilterRules(
 	users types.Users,
 	nodes views.Slice[types.NodeView],
 ) ([]tailcfg.FilterRule, error) {
-	if pol == nil {
+	if pol == nil || pol.ACLs == nil {
 		return tailcfg.FilterAllowAll, nil
 	}
 

hscontrol/policy/v2/policy_test.go

@@ -40,8 +40,8 @@ func TestPolicyManager(t *testing.T) {
 			name:         "empty-policy",
 			pol:          "{}",
 			nodes:        types.Nodes{},
-			wantFilter:   nil,
-			wantMatchers: []matcher.Match{},
+			wantFilter:   tailcfg.FilterAllowAll,
+			wantMatchers: matcher.MatchesFromFilterRules(tailcfg.FilterAllowAll),
 		},
 	}