Memory leak
A lot of following exceptions we get in JetBrains:

```
Editor of class com.intellij.openapi.editor.impl.EditorImpl hasn't been released:

com.intellij.openapi.util.TraceableDisposable.ObjectNotDisposedException: See stack trace responsible for creation of unreleased object below 
	at com.intellij.openapi.editor.impl.EditorImpl.<init>(EditorImpl.java:156)
	at com.intellij.openapi.editor.impl.EditorFactoryImpl.createEditor(EditorFactoryImpl.java:220)
	at com.intellij.openapi.editor.impl.EditorFactoryImpl.createEditor(EditorFactoryImpl.java:195)
	at mobi.hsz.idea.gitignore.util.Utils.createPreviewEditor(Utils.java:369)
	at mobi.hsz.idea.gitignore.ui.untrackFiles.UntrackFilesDialog.createCenterPanel(UntrackFilesDialog.java:197)
	at com.intellij.openapi.ui.DialogWrapper.init(DialogWrapper.java:1308)
	at mobi.hsz.idea.gitignore.ui.untrackFiles.UntrackFilesDialog.<init>(UntrackFilesDialog.java:139)
	at mobi.hsz.idea.gitignore.TrackedIgnoredFilesComponent$1.hyperlinkUpdate(TrackedIgnoredFilesComponent.java:125)
	at com.intellij.notification.impl.ui.NotificationsUtil$1.hyperlinkUpdate(NotificationsUtil.java:155)
	at javax.swing.JEditorPane.fireHyperlinkUpdate(JEditorPane.java:342)
	at javax.swing.text.html.HTMLEditorKit$LinkController.activateLink(HTMLEditorKit.java:875)
	at javax.swing.text.html.HTMLEditorKit$LinkController.mouseClicked(HTMLEditorKit.java:674)
	at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:270)
	at java.awt.Component.processMouseEvent(Component.java:6544)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
	at java.awt.Component.processEvent(Component.java:6306)
	at java.awt.Container.processEvent(Container.java:2237)
	at java.awt.Component.dispatchEventImpl(Component.java:4897)
	at java.awt.Container.dispatchEventImpl(Container.java:2295)
	at java.awt.Component.dispatchEvent(Component.java:4719)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4889)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4535)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4467)
	at java.awt.Container.dispatchEventImpl(Container.java:2281)
	at java.awt.Window.dispatchEventImpl(Window.java:2746)
	at java.awt.Component.dispatchEvent(Component.java:4719)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:764)
	at java.awt.EventQueue.access$500(EventQueue.java:98)
	at java.awt.EventQueue$3.run(EventQueue.java:715)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:90)
	at java.awt.EventQueue$4.run(EventQueue.java:737)
	at java.awt.EventQueue$4.run(EventQueue.java:735)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:734)
	at com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.java:821)
	at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:645)
	at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:365)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

```