more null fixes

src/main/java/ru/erius/lab5/commandline/PeopleDatabaseCommands.java

@@ -143,7 +143,7 @@ public final class PeopleDatabaseCommands {
     public static void sumOfHeight(PeopleDatabase peopleDatabase) {
         int sum = peopleDatabase.getCollection()
                 .stream()
-                .mapToInt(Person::getHeight)
+                .mapToInt(p -> p.getHeight() == null ? 0 : p.getHeight())
                 .sum();
         System.out.println("Сумма ростов всех людей в коллекции - " + sum);
     }

src/main/java/ru/erius/lab5/data/Location.java

@@ -73,7 +73,7 @@ public class Location implements Comparable<Location> {
      */
     @Override
     public int compareTo(Location other) {
-        return Comparator.comparing(Location::getName)
+        return Comparator.comparing(Location::getName, Comparator.nullsFirst(String::compareTo))
                 .thenComparing(Location::distance)
                 .compare(this, other);
     }

src/main/java/ru/erius/lab5/data/Person.java

@@ -174,8 +174,8 @@ public class Person implements Comparable<Person> {
     @Override
     public int compareTo(Person other) {
         return Comparator.comparing(Person::getName)
-                .thenComparing(Person::getPassportID)
-                .thenComparing(Person::getHeight)
+                .thenComparing(Person::getPassportID, Comparator.nullsFirst(String::compareTo))
+                .thenComparing(Person::getHeight, Comparator.nullsFirst(Integer::compareTo))
                 .thenComparing(Person::getCreationDate)
                 .thenComparing(p -> p.getNationality().toString())
                 .thenComparing(Person::getLocation)