feat-fix: fix the repl being broken

from [this situation](#718 (comment)), good job us

src/flowr.ts

@@ -5,6 +5,7 @@
  * Otherwise, it will start a REPL that can call these scripts and return their results repeatedly.
  */
 import { log, LogLevel } from './util/log'
+import type { RShellOptions } from './r-bridge'
 import { RShell } from './r-bridge'
 import type { OptionDefinition } from 'command-line-usage'
 import commandLineUsage from 'command-line-usage'
@@ -90,15 +91,18 @@ setConfigFile(undefined, options['config-file'] ?? defaultConfigFile, true)
 
 function retrieveShell(): RShell {
 	// we keep an active shell session to allow other parse investigations :)
-	return new RShell({
+	let opts: Partial<RShellOptions> = {
 		revive:   'always',
 		onRevive: (code, signal) => {
 			const signalText = signal == null ? '' : ` and signal ${signal}`
 			console.log(formatter.format(`R process exited with code ${code}${signalText}. Restarting...`, { color: Colors.Magenta, effect: ColorEffect.Foreground }))
 			console.log(italic(`If you want to exit, press either Ctrl+C twice, or enter ${bold(':quit')}`))
-		},
-		pathToRExecutable: options['r-path']
-	})
+		}
+	}
+	if(options['r-path']) {
+		opts = { ...opts, pathToRExecutable: options['r-path'] }
+	}
+	return new RShell(opts)
 }
 
 async function mainRepl() {