Address 4639

Make sure attribute "layer_name" always exists - even for PDFs without Optional Content.

Author: JorjMcKie

src/__init__.py

@@ -18836,6 +18836,7 @@ def __init__(self, result, layers):
         super().__init__()
         self.result = result
         self.layers = layers
+        self.layer_name = ""
         self.use_virtual_fill_path()
         self.use_virtual_stroke_path()
         self.use_virtual_fill_text()