fix merge

Author: XingY

api/src/org/labkey/api/dataiterator/ExistingRecordDataIterator.java

@@ -153,6 +153,8 @@ public Supplier<Object> getSupplier(int i)
     @Override
     public Object get(int i)
     {
+        assert(i <= existingColIndex);
+
         if (i<existingColIndex)
             return _delegate.get(i);
         Integer rowNumber = asInteger(_delegate.get(0));

experiment/src/org/labkey/experiment/api/ExpDataClassDataTableImpl.java

@@ -1095,6 +1095,11 @@ else if (Column.ClassId.name().equalsIgnoreCase(name))
                 step0.addColumn(nameCol, (Supplier<String>)() -> null);
             }
 
+            if (context.getSelectIds() && !columnNameMap.containsKey(RowId.name()))
+            {
+                step0.addNullColumn(RowId.name(), JdbcType.INTEGER);
+            }
+
             ColumnInfo lsidCol = expData.getColumn("lsid");
 
             // TODO: validate dataFileUrl column, it will be saved later