Fix T77022: node wranger error with texture files on different drives

Principled texture setup with relative path option would lead to this,
silently use an absolute path instead like other Blender operators.

Differential Revision: https://developer.blender.org/D12221

node_wrangler.py

@@ -2716,7 +2716,7 @@ class NWAddPrincipledSetup(Operator, NWBase, ImportHelper):
 
     relative_path: BoolProperty(
         name='Relative Path',
-        description='Select the file relative to the blend file',
+        description='Set the file path relative to the blend file, when possible',
         default=True
     )
 
@@ -2816,10 +2816,10 @@ class NWAddPrincipledSetup(Operator, NWBase, ImportHelper):
         import_path = self.directory
         if self.relative_path:
             if bpy.data.filepath:
-                import_path = bpy.path.relpath(self.directory)
-            else:
-                self.report({'WARNING'}, 'Relative paths cannot be used with unsaved scenes!')
-                print('Relative paths cannot be used with unsaved scenes!')
+                try:
+                    import_path = bpy.path.relpath(self.directory)
+                except ValueError:
+                    pass
 
         # Add found images
         print('\nMatched Textures:')