Fix mcp run script arg handling

app/src/main/java/io/xpipe/app/beacon/mcp/McpToolHandler.java

@@ -123,6 +123,14 @@ public interface McpToolHandler
             return b;
         }
 
+        public Optional<FilePath> getOptionalFilePath(ShellControl sc, String key) throws Exception {
+            if (getOptionalStringArgument(key).isEmpty()) {
+                return Optional.empty();
+            }
+
+            return Optional.of(getFilePath(sc, key));
+        }
+
         public FilePath getFilePath(ShellControl sc, String key) throws Exception {
             var s = getStringArgument(key);
             var path = FilePath.parse(s);

app/src/main/java/io/xpipe/app/beacon/mcp/McpTools.java

@@ -434,12 +434,13 @@ public final class McpTools {
                 .tool(tool)
                 .callHandler(McpToolHandler.of((req) -> {
                     var system = req.getStringArgument("system");
-                    var script = req.getDataStoreRef("script");
-                    var arguments = req.getStringArgument("arguments");
+                    var script = req.getDataStoreRef(req.getStringArgument("script"));
+                    var arguments = req.getOptionalStringArgument("arguments").orElse(null);
 
                     var shellStore = req.getShellStoreRef(system, true);
                     var shellSession = AppBeaconServer.get().getCache().getOrStart(shellStore);
-                    var directory = req.getFilePath(shellSession.getControl(), "directory");
+                    var directory = req.getOptionalFilePath(shellSession.getControl(), "directory")
+                            .orElse(null);
 
                     var clazz = Class.forName(
                             AppExtensionManager.getInstance()