fix(dialogs): Make sure conflict dialog is loaded before adding conflicts

Fixes a possible race condition where conflicts are added and the dialog
loading finishes only afterwards.

The race condition sometimes led to missing files in the conflict dialog
when uploading several existing files at once.

Fixes: #45661

Author: mejo-

core/src/OC/dialogs.js

@@ -918,27 +918,28 @@ const Dialogs = {
 		var dialogName = 'oc-dialog-fileexists-content'
 		var dialogId = '#' + dialogName
 		if (this._fileexistsshown) {
-			// add conflict
-
-			var $conflicts = $(dialogId + ' .conflicts')
-			addConflict($conflicts, original, replacement)
-
-			var count = $(dialogId + ' .conflict').length
-			var title = n('core',
-				'{count} file conflict',
-				'{count} file conflicts',
-				count,
-				{ count: count }
-			)
-			$(dialogId).parent().children('.oc-dialog-title').text(title)
-
-			// recalculate dimensions
-			$(window).trigger('resize')
-			dialogDeferred.resolve()
+			this._fileexistsshown.then(() => {
+				// add conflict
+
+				var $conflicts = $(dialogId + ' .conflicts')
+				addConflict($conflicts, original, replacement)
+
+				var count = $(dialogId + ' .conflict').length
+				var title = n('core',
+					'{count} file conflict',
+					'{count} file conflicts',
+					count,
+					{ count: count }
+				)
+				$(dialogId).parent().children('.oc-dialog-title').text(title)
+
+				// recalculate dimensions
+				$(window).trigger('resize')
+				dialogDeferred.resolve()
+			})
 		} else {
 			// create dialog
-			this._fileexistsshown = true
-			$.when(this._getFileExistsTemplate()).then(function($tmpl) {
+			this._fileexistsshown = $.when(this._getFileExistsTemplate()).then(function($tmpl) {
 				var title = t('core', 'One file conflict')
 				var $dlg = $tmpl.octemplate({
 					dialog_name: dialogName,