Fix null return value in NamedEntity.toString

src/main/java/org/springframework/samples/petclinic/model/NamedEntity.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.samples.petclinic.model;
 
+import java.util.Objects;
+
 import javax.annotation.Nullable;
 import javax.persistence.Column;
 import javax.persistence.MappedSuperclass;
@@ -44,7 +46,7 @@ public void setName(@Nullable String name) {
 
     @Override
     public String toString() {
-        return this.getName();
+        return Objects.toString(getName());
     }
 
 }

src/test/java/org/springframework/samples/petclinic/model/NamedEntityTests.java

@@ -0,0 +1,12 @@
+package org.springframework.samples.petclinic.model;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class NamedEntityTests {
+    @Test
+    public void toStringReturnsNonNullString() {
+        assertThat(new Pet().toString()).isEqualTo("null");
+    }
+}