Fix some React warnings (#10989)

app/javascript/mastodon/components/autosuggest_textarea.js

@@ -201,7 +201,7 @@ export default class AutosuggestTextarea extends ImmutablePureComponent {
     }
 
     return [
-      <div className='compose-form__autosuggest-wrapper'>
+      <div className='compose-form__autosuggest-wrapper' key='autosuggest-wrapper'>
         <div className='autosuggest-textarea'>
           <label>
             <span style={{ display: 'none' }}>{placeholder}</span>
@@ -226,7 +226,8 @@ export default class AutosuggestTextarea extends ImmutablePureComponent {
         </div>
         {children}
       </div>,
-      <div className='autosuggest-textarea__suggestions-wrapper'>
+
+      <div className='autosuggest-textarea__suggestions-wrapper' key='suggestions-wrapper'>
         <div className={`autosuggest-textarea__suggestions ${suggestionsHidden || suggestions.isEmpty() ? '' : 'autosuggest-textarea__suggestions--visible'}`}>
           {suggestions.map(this.renderSuggestion)}
         </div>

app/javascript/mastodon/features/compose/components/compose_form.js

@@ -33,10 +33,6 @@ const messages = defineMessages({
 export default @injectIntl
 class ComposeForm extends ImmutablePureComponent {
 
-  setRef = c => {
-    this.composeForm = c;
-  };
-
   static contextTypes = {
     router: PropTypes.object,
   };
@@ -119,8 +115,10 @@ class ComposeForm extends ImmutablePureComponent {
   }
 
   handleFocus = () => {
+    if (this.composeForm) {
       this.composeForm.scrollIntoView();
     }
+  }
 
   componentDidUpdate (prevProps) {
     // This statement does several things:
@@ -163,6 +161,10 @@ class ComposeForm extends ImmutablePureComponent {
     this.spoilerText = c;
   }
 
+  setRef = c => {
+    this.composeForm = c;
+  };
+
   handleEmojiPick = (data) => {
     const { text }     = this.props;
     const position     = this.autosuggestTextarea.textarea.selectionStart;