.exact modifier : Failed to generate render function

[rcocco]

Version

2.6.14

Reproduction link

https://template-explorer.vuejs.org/#%3Cbutton%20%40keydown.ctrl.shift.alt.meta.exact%3D%22console.log(%24event)%22%3EClick%3C%2Fbutton%3E

Steps to reproduce

use v-on with .ctrl.shift.alt.meta.exact modifiers

What is expected?

added event listener successfully

What is actually happening?

[Vue warn]: Failed to generate render function:
SyntaxError: Unexpected token ')' in

---

compiler generates if()return null; that's a syntax error.

 else if (key === 'exact') {
          var modifiers = (handler.modifiers);
          genModifierCode += genGuard(
            ['ctrl', 'shift', 'alt', 'meta']
              .filter(function (keyModifier) { return !modifiers[keyModifier]; })
              .map(function (keyModifier) { return ("$event." + keyModifier + "Key"); })
              .join('||')
          );
        }

[posva]

This should be an easy fix in the compiler: avoiding adding that last if when the condition is empty