prevent nil pointer dereference on script execution error

[mateeaaa]

Summary

This PR fixes a runtime panic (nil pointer dereference) that occurs in startScriptInBackground when a configured custom script fails to execute due to an operating system or path error rather than returning a standard process exit code.

Root Cause Analysis

In control_server.go, the background goroutine executes custom scripts via exec.Command(...) and handles errors returned by cmd.CombinedOutput().

When cmd.CombinedOutput() returns an error that is not an *exec.ExitError (for instance, os.ErrNotExist / exec.ErrNotFound if the binary does not exist on $PATH, or an os.PathError due to permission issues):

1. errors.As(err, &exitError) evaluates to false.
2. The exitError pointer remains nil.
3. Inside the else block, exitError.ExitCode() is called to populate the structured log fields.
4. Calling any method on a nil pointer receiver causes an unhandled runtime panic (invalid memory address or nil pointer dereference), which terminates the entire application process.

Solution

Replace the call to exitError.ExitCode() with defaultExitCode in the else block logging payload. The variable defaultExitCode is already defined and set to 1 right above the branch.

Changes Made

• Modified control_server.go at line 501: pass defaultExitCode instead of exitError.ExitCode() when logging errors for non-ExitError failures.