Reading commit history for empty sub conflict regions will throw errors

[kpatenio]

If a sub conflict region is empty (see example below), MergeConflictService will try to read commit logs even though none exist since no changes were made in this region. Update the implementation to fix this.

Example:

public class Test {

    private String testAttribute1;

    public void sayHelloThere() {
<<<<<<< HEAD
=======
        causeMethodoExtraction();
    }

    public void causeMethodoExtraction() {
>>>>>>> testBranch1
        System.out.println("Hello there!");
    }
}