lib: Don't suppress errors from inside the DataFile context manager

And fix up the trackdb to check if the file exists before attempting to
unpickle.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

lib/data.py

@@ -34,7 +34,7 @@ class DataFile:
             if self.mode == WRITE:
                 self.temp.replace(self.path)
             self.file = None
-        return True
+        return exp_type == None
 
     def exists(self):
         return self.path.exists()

trackdb/__init__.py

@@ -65,7 +65,8 @@ def save(*args):
 def load():
     global library_paths
     with data.DataFile(db_file, data.READ) as f:
-        (library.NextID, library_paths) = f.unpickle()
+        if f.exists():
+            (library.NextID, library_paths) = f.unpickle()
 
 def __register_callbacks():
     LibraryAdded.register(save)