Remove unneeded null checks

h2/src/main/org/h2/command/dml/MergeUsing.java

@@ -253,15 +253,11 @@ public class MergeUsing extends Prepared {
         // clear list of source table keys & rowids we have processed already
         targetRowidsRemembered.clear();
 
-        if (targetTableFilter != null) {
         targetTableFilter.startQuery(session);
         targetTableFilter.reset();
-        }
 
-        if (sourceTableFilter != null) {
         sourceTableFilter.startQuery(session);
         sourceTableFilter.reset();
-        }
 
         sourceQueryRowNumber = 0;
         checkRights();