fix: revert project files free (already freed in init)

src/file.c

@@ -133,5 +133,6 @@ void file_write(const char *path, const StringArray *lines) {
 void file_free(File *file) {
   if (!file->error && file->content != NULL) {
     free(file->content);
+    file->content = NULL;
   }
 }

src/project.c

@@ -144,9 +144,7 @@ void project_reload(Project *project, void (*reload_callback)(unsigned int)) {
 
 void project_free(Project *project) {
   for (unsigned int i = 0; i < project->frag_count; i++) {
-    for (unsigned int j = 0; j < MAX_SUB_FILE + 1; j++) {
-      file_free(&project->fragment_shaders[i][j]);
-    }
+    file_free(&project->fragment_shaders[i][0]);
   }
 
   config_file_free(&project->config);