Pull request: home: fix 8 to 9 migration

Updates #2988.

Squashed commit of the following:

commit 1b9f145be0dbcca9848e02942cea294315baa9cc
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Tue Apr 20 18:41:05 2021 +0300

    home: fix 8 to 9 migration

internal/home/upgrade.go

@@ -490,7 +490,16 @@ func upgradeSchema8to9(diskConf yobj) (err error) {
 		return fmt.Errorf("unexpected type of dns: %T", dnsVal)
 	}
 
-	autohostTLDVal := dns["autohost_tld"]
+	autohostTLDVal, ok := dns["autohost_tld"]
+	if !ok {
+		// This happens when upgrading directly from v0.105.2, because
+		// dns.autohost_tld was never set to any value.  Go on and leave
+		// it that way.
+		//
+		// See https://github.com/AdguardTeam/AdGuardHome/issues/2988.
+		return nil
+	}
+
 	autohostTLD, ok := autohostTLDVal.(string)
 	if !ok {
 		return fmt.Errorf("undexpected type of dns.autohost_tld: %T", autohostTLDVal)