#16 -- Fix npe

src/main/java/ru/ulstu/extractor/model/Branch.java

@@ -9,6 +9,7 @@ import javax.persistence.FetchType;
 import javax.persistence.JoinColumn;
 import javax.persistence.ManyToOne;
 import javax.persistence.OneToMany;
+import java.util.ArrayList;
 import java.util.List;
 
 @Entity
@@ -21,7 +22,7 @@ public class Branch extends BaseEntity {
     @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
     @JoinColumn(name = "branch_id", unique = true)
     @Fetch(FetchMode.SUBSELECT)
-    private List<Commit> commits;
+    private List<Commit> commits = new ArrayList<>();
 
     public Branch() {
     }