[USERENV] LoadUserProfileW(): Improve handling of lpProfileInfo->lpProfilePath (reactos#8321)

- As mentioned in the previous MSGINA commit aa67222,
  `lpProfilePath` specifies the path to a *roaming* user profile,
  for example on a domain server, if any. It is then used to create
  a local image (copy) of the profile on the local computer.

  HOWEVER (ReactOS HACK):
  We currently don't implement this in ReactOS; instead, we use it
  directly as *the* user's profile path, without doing any copy...

- Yes, MS Windows allows `lpProfileInfo->lpProfilePath` to be NULL :)

Author: HBelusca

dll/win32/userenv/profile.c

@@ -2007,7 +2007,7 @@ LoadUserProfileW(
     _Inout_ LPPROFILEINFOW lpProfileInfo)
 {
     WCHAR szUserHivePath[MAX_PATH];
-    DWORD dwLength = _countof(szUserHivePath);
+    DWORD dwLength;
     PTOKEN_USER UserSid = NULL;
     UNICODE_STRING SidString = { 0, 0, NULL };
     HANDLE hProfileMutex = NULL;
@@ -2055,24 +2055,33 @@ LoadUserProfileW(
     {
         DPRINT1("Loading profile %S\n", SidString.Buffer);
 
+        /*
+         * NOTE: lpProfilePath specifies the path to a *roaming* user profile,
+         * for example on a domain server, if any. It is then used to create
+         * a local image (copy) of the profile on the local computer.
+         *
+         * FIXME: We currently don't implement this in ReactOS; instead, we use
+         * it directly as *the* user's profile path, without doing any copy...
+         */
         if (lpProfileInfo->lpProfilePath)
         {
             /* Use the caller's specified roaming user profile path */
             StringCbCopyW(szUserHivePath, sizeof(szUserHivePath), lpProfileInfo->lpProfilePath);
         }
         else
         {
-            /* FIXME: check if MS Windows allows lpProfileInfo->lpProfilePath to be NULL */
+            /* Build a default user profile path */
+            dwLength = _countof(szUserHivePath);
             if (!GetProfilesDirectoryW(szUserHivePath, &dwLength))
             {
-                DPRINT1("GetProfilesDirectoryW() failed (error %ld)\n", GetLastError());
+                DPRINT1("GetProfilesDirectoryW() failed (Error %ld)\n", GetLastError());
                 goto cleanup;
             }
+            StringCbCatW(szUserHivePath, sizeof(szUserHivePath), L"\\");
+            StringCbCatW(szUserHivePath, sizeof(szUserHivePath), lpProfileInfo->lpUserName);
         }
 
         /* Create user hive name */
-        StringCbCatW(szUserHivePath, sizeof(szUserHivePath), L"\\");
-        StringCbCatW(szUserHivePath, sizeof(szUserHivePath), lpProfileInfo->lpUserName);
         StringCbCatW(szUserHivePath, sizeof(szUserHivePath), L"\\ntuser.dat");
         DPRINT("szUserHivePath: %S\n", szUserHivePath);