Don't iterate over advertised refs when HEAD is null

Moves the check from inside the loop to outside the loop
and returns immediately if the HEAD advertisded ref is null

Change-Id: I539da6cafb4f73610b8e00259e32bd4d57f4f4cc

org.eclipse.jgit/src/org/eclipse/jgit/api/CloneCommand.java

@@ -226,14 +226,14 @@ public class CloneCommand extends TransportCommand<CloneCommand, Git> {
 	}
 
 	private Ref findBranchToCheckout(FetchResult result) {
-		Ref foundBranch = null;
 		final Ref idHEAD = result.getAdvertisedRef(Constants.HEAD);
+		if (idHEAD == null)
+			return null;
+		Ref foundBranch = null;
 		for (final Ref r : result.getAdvertisedRefs()) {
 			final String n = r.getName();
 			if (!n.startsWith(Constants.R_HEADS))
 				continue;
-			if (idHEAD == null)
-				continue;
 			if (r.getObjectId().equals(idHEAD.getObjectId())) {
 				foundBranch = r;
 				break;