Dialogs now properly destroyed and removed from DOM when closed

Ensures dialogs are immediately removed from DOM when closed.
Previously, dialogs were destroyed but not removed causing possibility of duplicate element IDs, so jQuery unitentionally selects and recreates old dialogs, thus  GUI._updateOkButtonStatus updates the wrong button.

js/core/GUI.js

@@ -255,6 +255,7 @@ export class GUI
 					// close is called by both buttons and when the user clicks on the cross:
 					close: function () {
 						//$.unblockUI();
+						$(this).dialog('destroy').remove();
 						self._dialogComponent.status = PsychoJS.Status.FINISHED;
 					}
 
@@ -313,8 +314,6 @@ export class GUI
 		showOK = true,
 		onOK
 	} = {}) {
-		// destroy previous dialog box:
-		this.destroyDialog();
 
 		let htmlCode;
 		let titleColour;
@@ -410,7 +409,7 @@ export class GUI
 				id: "buttonOk",
 				text: "Ok",
 				click: function() {
-					$(this).dialog("close");
+					$(this).dialog("destroy").remove();
 
 					// execute callback function:
 					if (typeof onOK !== 'undefined')
@@ -504,24 +503,6 @@ export class GUI
 	}
 
 
-	/**
-	 * Destroy the currently opened dialog box.
-	 *
-	 * @name module:core.GUI#dialog
-	 * @function
-	 * @public
-	 */
-	destroyDialog()
-	{
-		if ($("#expDialog").length) {
-			$("#expDialog").dialog("destroy");
-		}
-		if ($("#msgDialog").length) {
-			$("#msgDialog").dialog("destroy");
-		}
-	}
-
-
 	/**
 	 * Listener for resource event from the [Server Manager]{@link ServerManager}.
 	 *

js/core/PsychoJS.js

@@ -387,9 +387,6 @@ export class PsychoJS
 					// close the window:
 					self._window.close();
 
-					// destroy dialog boxes:
-					self._gui.destroyDialog();
-
 					// remove everything from the browser window:
 					while (document.body.hasChildNodes())
 						document.body.removeChild(document.body.lastChild);