Removed unnecessary invariant usage

src/component/base/DraftEditor.react.js

@@ -354,7 +354,6 @@ class DraftEditor extends React.Component {
     const scrollParent = Style.getScrollParent(editorNode);
     const {x, y} = scrollPosition || getScrollPosition(scrollParent);
 
-    invariant(editorNode, 'Missing editorNode');
     invariant(
       editorNode instanceof HTMLElement,
       'editorNode is not an HTMLElement',
@@ -382,7 +381,6 @@ class DraftEditor extends React.Component {
 
   _blur(): void {
     const editorNode = ReactDOM.findDOMNode(this.refs.editor);
-    invariant(editorNode, 'Missing editorNode');
     invariant(
       editorNode instanceof HTMLElement,
       'editorNode is not an HTMLElement',

src/component/contents/DraftEditorBlock.react.js

@@ -112,7 +112,6 @@ class DraftEditorBlock extends React.Component {
         );
       }
     } else {
-      invariant(blockNode, 'Missing blockNode');
       invariant(
         blockNode instanceof HTMLElement,
         'blockNode is not an HTMLElement',

src/component/contents/DraftEditorTextNode.react.js

@@ -71,7 +71,6 @@ class DraftEditorTextNode extends React.Component {
   shouldComponentUpdate(nextProps: Props): boolean {
     const node = ReactDOM.findDOMNode(this);
     const shouldBeNewline = nextProps.children === '';
-    invariant(node, 'Missing node');
     invariant(node instanceof Element, 'node is not an Element');
     if (shouldBeNewline) {
       return !isNewline(node);