Revert "Don’t override lineOverdrawMargin with null"

This reverts commit 04cb43d657.

src/text-editor-element.coffee

@@ -15,6 +15,7 @@ class TextEditorElement extends HTMLElement
   componentDescriptor: null
   component: null
   attached: false
+  lineOverdrawMargin: null
   focusOnAttach: false
 
   createdCallback: ->
@@ -109,6 +110,7 @@ class TextEditorElement extends HTMLElement
       rootElement: @rootElement
       stylesElement: @stylesElement
       editor: @model
+      lineOverdrawMargin: @lineOverdrawMargin
       useShadowDOM: @useShadowDOM
     )
     @component = React.renderComponent(@componentDescriptor, @rootElement)