CLOUDSTACK-8749: Add checks to prevent malformed/unexpected input

Based on @jburwell's comment on PR #718

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>

Author: yadvr

plugins/hypervisors/kvm/src/com/cloud/hypervisor/kvm/resource/BridgeVifDriver.java

@@ -26,6 +26,7 @@
 
 import javax.naming.ConfigurationException;
 
+import com.google.common.base.Strings;
 import org.apache.log4j.Logger;
 import org.libvirt.LibvirtException;
 
@@ -286,7 +287,11 @@ private void deleteExitingLinkLocalRouteTable(String linkLocalBr) {
             String[] lines = parser.getLines().split("\\n");
             for (String line : lines) {
                 String[] tokens = line.split(" ");
-                if (!tokens[2].equalsIgnoreCase(linkLocalBr)) {
+                if (tokens != null && tokens.length < 2) {
+                    continue;
+                }
+                final String device = tokens[2];
+                if (!Strings.isNullOrEmpty(device) && !device.equalsIgnoreCase(linkLocalBr)) {
                     Script.runSimpleBashScript("ip route del " + NetUtils.getLinkLocalCIDR() + " dev " + tokens[2]);
                 } else {
                     foundLinkLocalBr = true;