Merge branch 'stable-4.11'

* stable-4.11:
  LFS: Fix potential NPE in LfsPrePushHook

Change-Id: If721bd18035870541d216d2dcd9d47484e9af3e5
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPrePushHook.java

@@ -180,6 +180,10 @@ public class LfsPrePushHook extends PrePushHook {
 			if (oid == null) {
 				oid = r.getObjectId();
 			}
+			if (oid == null) {
+				// ignore (e.g. symbolic, ...)
+				continue;
+			}
 			RevObject o = walk.parseAny(oid);
 			if (o.getType() == Constants.OBJ_COMMIT
 					|| o.getType() == Constants.OBJ_TAG) {