rstudioapi::showDialog returns NA link when url param is NULL (Default)

RStudio IDE
1 
rstudioapi::showDialog(title = 'error',
                           message = 'Right is used on only one line')

creates this dialogue

01
01806×290 12 KB

same with

rstudioapi::showDialog(title = 'error',
                           message = 'Right is used on only one line',
url='')

sessionInfo()
R version 3.3.3 (2017-03-06)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: macOS  10.13

RStudio.Version()
$mode
[1] "desktop"

$version
[1] ‘1.1.383’