add attach handler for detach when widget already attached #1003

Author: rore22x

gwt-material/src/main/java/gwt/material/design/client/ui/MaterialTooltip.java

@@ -206,6 +206,11 @@ public void setWidget(final Widget widget) {
         }
 
         if (this.widget.isAttached()) {
+            widget.addAttachHandler(event -> {
+                if (!event.isAttached()) {
+                    unload();
+                }
+            });
             reload();
         } else {
             // Smart detect the attachment and detachment of widget to update the tooltip