AutomationEditor: update pause icon manually

As we have a special semantic for automation pattern playback (i.e. we
don't playback the pattern itself but its container component like
Song Editor, Piano Roll etc.).

Closes #292.

src/gui/AutomationEditor.cpp

@@ -1907,6 +1907,8 @@ void AutomationEditor::play()
 			engine::getSong()->togglePause();
 		}
 	}
+
+	setPauseIcon( engine::getSong()->isPlaying() );
 }