Fixed multi-object export texture corruption error

This fixes the bug where exporting 3 or more objects would result in
one or more objects have corrupted texture coordinates

src/__init__.py

@@ -2,7 +2,7 @@ bl_info = {
     'name': 'ASCII Scene Export (ASE)',
     'description': 'Export ASE (ASCII Scene Export) files',
     'author': 'Colin Basnett (Darklight Games)',
-    'version': (1, 2, 0),
+    'version': (1, 2, 1),
     'blender': (2, 90, 0),
     'location': 'File > Import-Export',
     'warning': 'This add-on is under development.',

src/builder.py

@@ -138,7 +138,7 @@ class ASEBuilder(object):
                         geometry_object.vertex_colors.append(tuple(color[0:3]))
 
             # Update data offsets for next iteration
-            geometry_object.texture_vertex_offset = len(mesh_data.loops)
+            geometry_object.texture_vertex_offset += len(mesh_data.loops)
             geometry_object.vertex_offset = len(geometry_object.vertices)
 
         if len(ase.geometry_objects) == 0: