Allow users to skip creating a directory

This is mostly useful if the previously defined libraries
don't exist. E.g., the library is on an external drive
that isn't plugged in.

steam_library_setup_tool.py

@@ -112,9 +112,6 @@ def writeLibraryInfo( self ):
                     except:
                         messagebox.showerror( "Error", "Error when creating directories" )
                         raise
-                else:
-                    messagebox.showerror( "Error", "Can not proceed without creating directories" )
-                    raise ValueError( "Can not proceed without creating directories" )
 
         info = vdf.load( open( self.library_vdf_path, 'r' ) )