Fix discovery NPE (#1430)

Signed-off-by: Chris Jackson <[email protected]>

Author: cdjackson

com.zsmartsystems.zigbee/src/main/java/com/zsmartsystems/zigbee/app/discovery/ZigBeeNetworkDiscoverer.java

@@ -402,8 +402,8 @@ private boolean getAssociatedNodes(final int networkAddress) throws InterruptedE
             final IeeeAddressResponse ieeeAddressResponse = response.getResponse();
             logger.debug("NWK Discovery for {} IeeeAddressRequest returned {}", String.format("%04X", networkAddress),
                     ieeeAddressResponse);
-            if (ieeeAddressResponse != null && ieeeAddressResponse.getStatus() == ZdoStatus.SUCCESS
-                    && startIndex == ieeeAddressResponse.getStartIndex()) {
+            if (ieeeAddressResponse != null && ieeeAddressResponse.getStatus() == ZdoStatus.SUCCESS &&
+                    ieeeAddressResponse.getStartIndex() != null && startIndex == ieeeAddressResponse.getStartIndex()) {
                 associatedDevices.addAll(ieeeAddressResponse.getNwkAddrAssocDevList());
 
                 startIndex += ieeeAddressResponse.getNwkAddrAssocDevList().size();

com.zsmartsystems.zigbee/src/test/java/com/zsmartsystems/zigbee/zdo/command/IeeeAddressResponseTest.java

@@ -8,6 +8,7 @@
 package com.zsmartsystems.zigbee.zdo.command;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
 
 import org.junit.Test;
 
@@ -41,6 +42,7 @@ public void testReceiveShort() {
         assertEquals(new IeeeAddress("0022A300001732BF"), addressResponse.getIeeeAddrRemoteDev());
         assertEquals(0x8001, (int) addressResponse.getClusterId());
         assertEquals(ZdoStatus.SUCCESS, addressResponse.getStatus());
+        assertNull(addressResponse.getStartIndex());
     }
 
     @Test