fix index out of range when quickly typing and or changing suggestions

completion.go

@@ -47,6 +47,8 @@ func (c *CompletionManager) GetSelectedSuggestion() (s Suggest, ok bool) {
  debug.Assert(false, "must not reach here")
  c.selected = -1
  return Suggest{}, false
+ } else if c.selected >= len(c.tmp) {
+ return Suggest{}, false
  }
  return c.tmp[c.selected], true
 }