fixed macro replacement

app/controllers/home.controller.js

                     .trim();
                 $scope.macros.forEach(function(macro)
                 {
-                    var regex = macro.latex.match(/[a-zA-Z0-9]$/) != null ? "([^a-zA-Z0-9])" : "";
+                    var regex = macro.latex.match(/[a-zA-Z0-9]$/) != null ? "([^a-zA-Z0-9])" : "()";
                     text = text.replace(new RegExp($scope.escapeRegExp(macro.latex) + regex, "g"), function($1, $2)
                     {
                         return macro.html + $2;