Fix unused throws CorruptObjectException from addTree

2262a794b4 removed throws CorruptObjectException, but was not
compiled under Eclipse and did not see errors generated by Eclipse.
Maven build silently ignored the unnecessary code.

Change-Id: I6e9014adcc604588e10e5963d13d0c6ef0e1c617

org.eclipse.jgit.test/tst/org/eclipse/jgit/attributes/AttributesNodeWorkingTreeIteratorTest.java

@@ -56,7 +56,6 @@ import java.util.Collections;
 import java.util.List;
 
 import org.eclipse.jgit.attributes.Attribute.State;
-import org.eclipse.jgit.errors.CorruptObjectException;
 import org.eclipse.jgit.junit.JGitTestUtil;
 import org.eclipse.jgit.junit.RepositoryTestCase;
 import org.eclipse.jgit.lib.FileMode;
@@ -253,7 +252,7 @@ public class AttributesNodeWorkingTreeIteratorTest extends RepositoryTestCase {
 		writeTrashFile(name, data.toString());
 	}
 
-	private TreeWalk beginWalk() throws CorruptObjectException {
+	private TreeWalk beginWalk() {
 		TreeWalk newWalk = new TreeWalk(db);
 		newWalk.addTree(new FileTreeIterator(db));
 		return newWalk;

org.eclipse.jgit.test/tst/org/eclipse/jgit/ignore/IgnoreNodeTest.java

@@ -55,7 +55,6 @@ import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Arrays;
 
-import org.eclipse.jgit.errors.CorruptObjectException;
 import org.eclipse.jgit.ignore.IgnoreNode.MatchResult;
 import org.eclipse.jgit.junit.RepositoryTestCase;
 import org.eclipse.jgit.lib.FileMode;
@@ -509,7 +508,7 @@ public class IgnoreNodeTest extends RepositoryTestCase {
 						.toString());
 	}
 
-	private void beginWalk() throws CorruptObjectException {
+	private void beginWalk() {
 		walk = new TreeWalk(db);
 		walk.addTree(new FileTreeIterator(db));
 	}