filesystem: fix checking for directory existence

Resolves #2504.

docs/tr2/CHANGELOG.md

@@ -1,4 +1,5 @@
 ## [Unreleased](https://github.com/LostArtefacts/TRX/compare/tr2-0.9.1...develop) - ××××-××-××
+- fixed music not working on certain Linux setups (#2504, regression from 0.2)
 
 ## [0.9.1](https://github.com/LostArtefacts/TRX/compare/tr2-0.9...tr2-0.9.1) - 2025-02-15
 - changed passport to be more responsive to player inputs (#1328)

src/libtrx/filesystem.c

@@ -152,7 +152,7 @@ const char *File_GetGameDirectory(void)
 bool File_DirExists(const char *path)
 {
     char *full_path = File_GetFullPath(path);
-    DIR *dir = opendir(path);
+    DIR *dir = opendir(full_path);
     Memory_FreePointer(&full_path);
     if (dir != nullptr) {
         closedir(dir);