Better cleanup on mount failures, as the idf api now seems to assign handle...

Better cleanup on mount failures, as the idf api now seems to assign handle and mountpoint before failing. Fixes #3265 (#3282)

libraries/FFat/src/FFat.cpp

@@ -58,6 +58,8 @@ bool F_Fat::begin(bool formatOnFail, const char * basePath, uint8_t maxOpenFiles
     esp_err_t err = esp_vfs_fat_spiflash_mount(basePath, partitionLabel, &conf, &_wl_handle);
     if(err){
         log_e("Mounting FFat partition failed! Error: %d", err);
+        esp_vfs_fat_spiflash_unmount(basePath, _wl_handle);
+        _wl_handle = WL_INVALID_HANDLE;
         return false;
     }
     _impl->mountpoint(basePath);