Replace /Applications/Docker/Docker Quickstart Terminal.app/Contents/Resources/Scripts/iterm.scpt with this.

## iterm.scpt
set itermRunning to (application "iTerm" is running)
set scriptPath to quoted form of POSIX path of ((path to me as text) & "::" & "start.sh")
set user_shell to do shell script "dscl /Search -read /Users/$USER UserShell | awk '{print $2}'"

tell application "iTerm"
    activate
    if not (exists window 1) or (itermRunning = false) then
        reopen
    end if

    try
        tell current window
            set newTab to (create tab with default profile)
            tell current session of newTab
                write text "bash --login " & scriptPath
            end tell
        end tell
    on error
        tell current session of (create window with default profile)
            write text "bash --login " & scriptPath
        end tell
    end try
end tell