Pull request: home: fix install panic

Closes #3596.

Squashed commit of the following:

commit e14f8795859cf775b360d4fe2f5c1d0eebb87ba6
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Tue Sep 14 17:49:48 2021 +0300

    home: fix install panic

CHANGELOG.md

@@ -49,8 +49,8 @@ and this project adheres to
 
 - The `systemd` service script will now create the `/var/log` directory when it
   doesn't exist ([#3579]).
-- Items in allowed clients, disallowed clients, and blocked hosts lists must
-  be unique ([#3419]).
+- Items in allowed clients, disallowed clients, and blocked hosts lists are now
+  required to be unique ([#3419]).
 - The TLS private key previously saved as a string isn't shown in API responses
   anymore ([#1898]).
 - Better OpenWrt detection ([#3435]).
@@ -115,7 +115,8 @@ In this release, the schema version has changed from 10 to 12.
 
 ### Fixed
 
-- Panic when upstream server responds with empty question section ([#3551]).
+- Panic when an upstream server responds with an empty question section
+  ([#3551]).
 - 9GAG blocking ([#3564]).
 - DHCP now follows RFCs more closely when it comes to response sending and
   option selection ([#3443], [#3538]).

internal/home/controlinstall.go

@@ -257,7 +257,8 @@ type applyConfigReq struct {
 	Password string            `json:"password"`
 }
 
-// Copy installation parameters between two configuration objects
+// copyInstallSettings copies the installation parameters between two
+// configuration structures.
 func copyInstallSettings(dst, src *configuration) {
 	dst.BindHost = src.BindHost
 	dst.BindPort = src.BindPort
@@ -307,7 +308,7 @@ func (web *Web) handleInstallConfigure(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	var curConfig *configuration
+	curConfig := &configuration{}
 	copyInstallSettings(curConfig, config)
 
 	Context.firstRun = false