🐛 Fix dom reader failing to append the node outside render view

lib/minimap-render-view.coffee

@@ -301,6 +301,12 @@ class MinimapRenderView extends ScrollView
       height: @getMinimapHeight()
     }
 
+  getDummyDOMRoot: (shadowRoot) ->
+    if shadowRoot
+      @minimapView.getEditorViewRoot()
+    else
+      @editorView
+
   # Returns a pixel position corresponding to a character's screen
   # position.
   #

lib/mixins/dom-styles-reader.coffee

@@ -2,8 +2,6 @@ Mixin = require 'mixto'
 
 module.exports =
 class DOMStylesReader extends Mixin
-  @domStylesCache: {}
-
   # Internal: This function insert a dummy element in the DOM to compute
   # its style, return the specified property, and remove the element
   # from the DOM.
@@ -16,6 +14,8 @@ class DOMStylesReader extends Mixin
   #
   # Returns a {String} of the property value.
   retrieveStyleFromDom: (scopes, property, shadowRoot=true, cache=true) ->
+    @ensureCache()
+
     key = scopes.join(' ')
 
     if cache and @constructor.domStylesCache[key]?[property]?
@@ -45,10 +45,11 @@ class DOMStylesReader extends Mixin
     unless @dummyNode?
       @dummyNode = document.createElement('span')
       @dummyNode.style.visibility = 'hidden'
-    if shadowRoot
-      @minimapView.getEditorViewRoot().appendChild(@dummyNode)
-    else
-      @editorView.appendChild(@dummyNode)
+
+    @getDummyDOMRoot(shadowRoot).appendChild(@dummyNode)
+
+  ensureCache: ->
+    @constructor.domStylesCache ?= {}
 
   invalidateCache: ->
     @constructor.domStylesCache = {}