[Bug] Fix null pointer when replay RollupJob (#4572)

When fe replay rollup job(v1) with deleted table, it will throw null pointer exception and exit.
This commit ignore this error and print a warning log to avoid fe exit.

Fixed #4571

Change-Id: I302b554a94d42aee645db6b224cd989e00cd3ca6

fe/fe-core/src/main/java/org/apache/doris/alter/RollupJob.java

@@ -903,6 +903,10 @@ public class RollupJob extends AlterJob {
         db.writeLock();
         try {
             OlapTable olapTable = (OlapTable) db.getTable(tableId);
+            if (olapTable == null) {
+                LOG.warn("table {} could not be found when replay rollup job", tableId);
+                return;
+            }
             olapTable.setState(OlapTableState.NORMAL);
         } finally {
             db.writeUnlock();