Prevent TypeError when parsing '=~' operator

lib/carto/tree/filterset.js

@@ -93,7 +93,7 @@ tree.Filterset.prototype.toJS = function(env) {
     }
     var attrs = "data";
     if (op === '=~') {
-        return attrs + "['" + filter.key.value  + "'].match(" + (val.is === 'string' ? "'" + val.toString().replace(/'/g, "\\'") + "'" : val) + ")";
+      return "(typeof " + attrs + "['" + filter.key.value  + "'] === 'string') && " + attrs + "['" + filter.key.value  + "'].match(" + (val.is === 'string' ? "'" + val.toString().replace(/'/g, "\\'") + "'" : val) + ")";
     }
     return attrs + "['" + filter.key.value  + "'] " + op + " " + (val.is === 'string' ? "'" + val.toString().replace(/'/g, "\\'") + "'" : val);
   }).join(' && ');

test/rendering_js.test.js

@@ -183,7 +183,7 @@ describe('RenderingJS', function() {
     assert.equal(st.args[2].args[0].value, 10);
   });
 
-  it("should not throw `ReferenceError`", function(){
+  it("should not throw `ReferenceError` with `=~` operator", function(){
     var css = [
       '#layer[name=~".*Cairo*"] {',
       '  marker-width: 14;',
@@ -196,4 +196,21 @@ describe('RenderingJS', function() {
       var value = layer.shader['marker-width'].style({ name: 'wadus' }, { zoom: 1 });
     });
   });
+ 
+  it("should not throw `TypeError` if left operand is not a `string` with operator `=~`", function(){
+    var css = [
+      '#layer[name=~1] {',
+      '  marker-width: 14;',
+      '}'
+    ].join('\n');
+
+    assert.doesNotThrow(function () {
+      var shader = (new carto.RendererJS({})).render(css);
+      var layer = shader.getLayers()[0];
+      var value = layer.shader['marker-width'].style({ name: 1 }, { zoom: 1 });
+      value = layer.shader['marker-width'].style({ name: null }, { zoom: 1 });
+      value = layer.shader['marker-width'].style({ name: undefined }, { zoom: 1 });
+      value = layer.shader['marker-width'].style({ name: true }, { zoom: 1 });
+    });
+  });
 });