don't crash when an action=nullptr (partial fix for #20)

src/data/action/value.cpp

@@ -149,7 +149,7 @@ TextValueAction* toggle_format_action(const TextValueP& value, const String& tag
 		new_value += _("</") + tag + _(">");
 		new_value += str.substr(end_i);
 	} else {
-		// we are inside this tag, _('remove') it
+		// we are inside this tag, 'remove' it
 		new_value =  str.substr(0, start_i);
 		new_value += _("</") + tag + _(">");
 		new_value += str.substr(start_i, end_i - start_i);

src/gui/value/editor.cpp

@@ -13,6 +13,8 @@
 // ----------------------------------------------------------------------------- : ValueEditor
 
 void ValueEditor::addAction(ValueAction* a) {
-	a->isOnCard(editor().getCard().get());
-	editor().addAction(a);
+	if (a) {
+		a->isOnCard(editor().getCard().get());
+		editor().addAction(a);
+	}
 }