OO-216: fix an issue with the id of single/multi select box

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

@@ -340,7 +340,8 @@ public class MultipleSelectionElementImpl extends FormItemImpl implements Multip
 			}
 		}
 		// create and add selectbox element
-		SelectboxComponent sssc = new SelectboxComponent(getFormItemId() + "_SELBOX", getName() + "_SELBOX", translator, this, keys, values, cssClasses);
+		String ssscId = getFormItemId() == null ? null : getFormItemId() + "_SELBOX";
+		SelectboxComponent sssc = new SelectboxComponent(ssscId, getName() + "_SELBOX", translator, this, keys, values, cssClasses);
 
 		formLayoutContainer.put(getName() + "_SELBOX", sssc);
 		formLayoutContainer.contextPut("selectbox", getName() + "_SELBOX");

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

@@ -303,7 +303,8 @@ public class SingleSelectionImpl extends FormItemImpl implements SingleSelection
 			}
 		}
 		//create and add selectbox element
-		SelectboxComponent sssc = new SelectboxComponent(getFormItemId() + "_SELBOX" , getName() + "_SELBOX", translator, this, keys, values, cssClasses);
+		String ssscId = getFormItemId() == null ? null : getFormItemId() + "_SELBOX";
+		SelectboxComponent sssc = new SelectboxComponent(ssscId , getName() + "_SELBOX", translator, this, keys, values, cssClasses);
 		formLayoutContainer.put(getName()+"_SELBOX", sssc);
 		formLayoutContainer.contextPut("selectbox", getName()+"_SELBOX");
 		//formComponentsNames.add(getName()+"_SELBOX");