code: function(paramSize, name) {
        this.context.aliases.helperMissing = 'helpers.helperMissing';
  
        var helper = this.lastHelper = this.setupHelper(paramSize, name);
        this.register('foundHelper', helper.name);
  
        this.pushStack("foundHelper ? foundHelper.call(" +
          helper.callParams + ") " + ": helperMissing.call(" +
          helper.helperMissingParams + ")");
      }
docs: [invokeHelper]  On stack, before: hash, inverse, program, params..., ... On stack, after: result of helper invocation  Pops off the helper's parameters, invokes the helper, and pushes the helper's return value onto the stack.  If the helper is not found, `helperMissing` is called.