OO-4366 Fixed table column selector with mandatory columns and only one

additionally selected column

src/main/java/org/olat/core/gui/components/form/flexible/impl/elements/table/FlexiTableElementImpl.java

@@ -106,6 +106,7 @@ public class FlexiTableElementImpl extends FormItemImpl implements FlexiTableEle
 	private boolean numOfRowsEnabled = true;
 	private boolean showAllRowsEnabled = false;
 	private boolean extendedSearchExpanded = false;
+	private boolean hasAlwaysVisibleColumns = false;
 	private int columnLabelForDragAndDrop;
 	private String emptyTableMessageKey = null;
 	
@@ -166,6 +167,10 @@ public class FlexiTableElementImpl extends FormItemImpl implements FlexiTableEle
 				enabledColumnIndex.add(Integer.valueOf(col.getColumnIndex()));
 			}
 		}
+		
+		if(enabledColumnIndex.size() > 0 ) {
+			hasAlwaysVisibleColumns = true;
+		}
 
 		String dispatchId = component.getDispatchID();
 		customButton = new FormLinkImpl(dispatchId + "_customButton", "rCustomButton", "", Link.BUTTON + Link.NONTRANSLATED);
@@ -1385,12 +1390,12 @@ public class FlexiTableElementImpl extends FormItemImpl implements FlexiTableEle
 	}
 	
 	protected void setCustomizedColumns(UserRequest ureq, Choice visibleColsChoice) {
-		List<Integer> visibleCols = visibleColsChoice.getSelectedRows();
-		if(visibleCols.size() > 1) {
+		List<Integer> chosenCols = visibleColsChoice.getSelectedRows();
+		if(chosenCols.size() > 1 || hasAlwaysVisibleColumns) {
 			VisibleFlexiColumnsModel model = (VisibleFlexiColumnsModel)visibleColsChoice.getModel();
 			for(int i=model.getRowCount(); i-->0; ) {
 				FlexiColumnModel col = model.getObject(i);
-				if(visibleCols.contains(Integer.valueOf(i))) {
+				if(chosenCols.contains(Integer.valueOf(i))) {
 					enabledColumnIndex.add(col.getColumnIndex());
 				} else {
 					enabledColumnIndex.remove(col.getColumnIndex());