Fix segfault when changing color of unexisting entity

src/interface/Settings_window.cpp

@@ -203,6 +203,10 @@ void Settings_window::color_changed(string name, QTableWidget *table, const QCol
     Session &S = Session::getSession();
     Palette *p = S.get_palette(name, palette_name);
     Color *old = p->get_color(state_name);
+    // Quick and dirty patch
+    if ( old == NULL ) {
+        old = new Color(1, 1, 1);
+    }
     QColor q(old->get_red()*255, old->get_green()*255, old->get_blue()*255);
 
     bool checked = qobject_cast<QCheckBox *>(table->cellWidget(row, 2))->checkState()== Qt::Checked;