IGNITE-29000 NPE can be raised from GridCachePartitionExchangeManager#lastAffinityChangedTopologyVersion (#13504)

Author: zstan

modules/core/src/main/java/org/apache/ignite/internal/processors/cache/GridCachePartitionExchangeManager.java

@@ -1052,11 +1052,14 @@ public boolean hasPendingServerExchange() {
     }
 
     /**
-     *
      * @param topVer Topology version.
-     * @return Last topology version before the provided one when affinity was modified.
+     * @return Last topology version before the provided one when affinity was modified or {@link AffinityTopologyVersion#NONE}
+     * if {@code topVer} is null.
      */
     public AffinityTopologyVersion lastAffinityChangedTopologyVersion(AffinityTopologyVersion topVer) {
+        if (topVer == null)
+            return NONE;
+
         if (topVer.topologyVersion() <= 0)
             return topVer;