Remove whitespace hack on empty post content

It's no longer necessary since the backend handles posts with empty
content fine and also fixes an odd whitespace when attachment links are
disabled.

src/components/post_status_form/post_status_form.js

@@ -169,9 +169,7 @@ const PostStatusForm = {
       if (this.submitDisabled) { return }
 
       if (this.newStatus.status === '') {
-        if (this.newStatus.files.length > 0) {
-          this.newStatus.status = '\u200b' // hack
-        } else {
+        if (this.newStatus.files.length === 0) {
           this.error = 'Cannot post an empty status with no files'
           return
         }