Fix leak minimap

lib/minimap-element.coffee

@@ -149,6 +149,7 @@ class MinimapElement extends HTMLElement
   destroy: ->
     @subscriptions.dispose()
     @detach()
+    @minimap = null
 
   #     ######   #######  ##    ## ######## ######## ##    ## ########
   #    ##    ## ##     ## ###   ##    ##    ##       ###   ##    ##
@@ -326,7 +327,7 @@ class MinimapElement extends HTMLElement
 
   # Internal: Performs the actual {MinimapElement} update.
   update: ->
-    return unless @attached and @isVisible() and not @minimap.isDestroyed()
+    return unless @attached and @isVisible() and @minimap?
 
     if @adjustToSoftWrap and @marginRight?
       @style.marginRight = @marginRight + 'px'
@@ -516,7 +517,7 @@ class MinimapElement extends HTMLElement
   startDrag: ({which, pageY}) ->
     # if which is 2
     #   @middleMousePressedOverCanvas({pageY})
-    return if @minimap.isDestroyed()
+    return unless @minimap
     return if which isnt 1 and which isnt 2
     {top} = @visibleArea.getBoundingClientRect()
     {top: offsetTop} = @getBoundingClientRect()
@@ -546,7 +547,7 @@ class MinimapElement extends HTMLElement
   #           offsetTop - The {MinimapElement} offset at the moment of the
   #                       drag start.
   drag: (e, initial) ->
-    return if @minimap.isDestroyed()
+    return unless @minimap
     return if e.which isnt 1 and e.which isnt 2
     y = e.pageY - initial.offsetTop - initial.dragOffset
 
@@ -563,7 +564,7 @@ class MinimapElement extends HTMLElement
   #           offsetTop - The {MinimapElement} offset at the moment of the
   #                       drag start.
   endDrag: (e, initial) ->
-    return if @minimap.isDestroyed()
+    return unless @minimap
     @dragSubscription.dispose()
 
   #     ######   ######   ######