Don't block for the EDT when an error is raised.

This is prone to race conditions if an error occurs when
the EDT is waiting on a lock owned by the erroring thread.

Fixes DMDirc/DMDirc#805

ui_swing/src/main/java/com/dmdirc/addons/ui_swing/components/statusbar/ErrorPanel.java

 
     @Override
     public void errorDeleted(final DisplayableError error) {
-        UIUtilities.invokeAndWait(this::checkErrors);
+        UIUtilities.invokeLater(this::checkErrors);
     }
 
     @Override
     public void errorAdded(final DisplayableError error) {
-        UIUtilities.invokeAndWait(this::checkErrors);
+        UIUtilities.invokeLater(this::checkErrors);
     }
 
     @Override