DirCache: Fix getEntriesWithin("") to not include null entries

The internal array may be longer than entryCnt, in this case the tail
of the array is padded with null entries. Do not return those to the
caller of getEntriesWithin().

Change-Id: I19efb05e103fab6b739ced407f6e28155a48dba6

org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCache.java

@@ -877,8 +877,8 @@ public class DirCache {
 	 */
 	public DirCacheEntry[] getEntriesWithin(String path) {
 		if (path.length() == 0) {
-			final DirCacheEntry[] r = new DirCacheEntry[sortedEntries.length];
-			System.arraycopy(sortedEntries, 0, r, 0, sortedEntries.length);
+			DirCacheEntry[] r = new DirCacheEntry[entryCnt];
+			System.arraycopy(sortedEntries, 0, r, 0, entryCnt);
 			return r;
 		}
 		if (!path.endsWith("/")) //$NON-NLS-1$