Fix crash loading from search path

Possible fix for #395

dtool/src/prc/configVariableSearchPath.I

@@ -229,9 +229,13 @@ get_num_directories() const {
 /**
  * Returns the nth directory on the search list.
  */
-INLINE const Filename &ConfigVariableSearchPath::
+INLINE Filename ConfigVariableSearchPath::
 get_directory(size_t n) const {
-  return get_value().get_directory(n);
+  Filename dir;
+  _lock.lock();
+  dir = _cache.get_directory(n);
+  _lock.unlock();
+  return dir;
 }
 
 /**

dtool/src/prc/configVariableSearchPath.h

@@ -66,7 +66,7 @@ PUBLISHED:
 
   INLINE bool is_empty() const;
   INLINE size_t get_num_directories() const;
-  INLINE const Filename &get_directory(size_t n) const;
+  INLINE Filename get_directory(size_t n) const;
   MAKE_SEQ(get_directories, get_num_directories, get_directory);
   MAKE_SEQ_PROPERTY(directories, get_num_directories, get_directory);
 

panda/src/pgraph/loader.cxx

@@ -207,7 +207,7 @@ load_file(const Filename &filename, const LoaderOptions &options) const {
 
   if (search) {
     // Look for the file along the model path.
-    const ConfigVariableSearchPath &model_path = get_model_path();
+    DSearchPath model_path(get_model_path());
     int num_dirs = model_path.get_num_directories();
     for (int i = 0; i < num_dirs; ++i) {
       Filename pathname(model_path.get_directory(i), this_filename);