tweak void styles, fix tests

packages/slate-react/src/components/void.js

@@ -128,20 +128,13 @@ class Void extends React.Component {
     const Tag = node.kind == 'block' ? 'div' : 'span'
     let style
 
-    if (!readOnly && node.kind == 'block') {
+    if (!readOnly) {
       style = {
-        display: 'block',
         height: '0',
         color: 'transparent'
       }
     }
 
-    if (!readOnly && node.kind == 'inline') {
-      style = {
-        color: 'transparent'
-      }
-    }
-
     this.debug('render', { props })
 
     return (

packages/slate-react/test/rendering/fixtures/custom-block-void.js

@@ -24,9 +24,11 @@ export const state = (
 export const output = `
 <div data-slate-editor="true" contenteditable="true" role="textbox">
   <div data-slate-void="true">
-    <span style="display:inline-block;vertical-align:top;width:0;height:0;color:transparent">
+    <div style="height:0;color:transparent">
+      <span>
         <span></span>
       </span>
+    </div>
     <div contenteditable="false">
       <img src="https://example.com/image.png">
     </div>

packages/slate-react/test/rendering/fixtures/custom-inline-void.js

@@ -32,9 +32,11 @@ export const output = `
       </span>
     </span>
     <span data-slate-void="true">
-      <span style="color:transparent">
+      <span style="height:0;color:transparent">
+        <span>
           <span></span>
         </span>
+      </span>
       <span contenteditable="false">
         <img>
       </span>