diff_evt breaks on empty lines

[marijnvdwerf]

If there's an empty line in symbol_addrs, diff_evt.py crashes instead of producing output

Traceback (most recent call last):
  File "/Users/marijn/Projects/papermario-jp/diff_evt.py", line 168, in <module>
    main()
  File "/Users/marijn/Projects/papermario-jp/diff_evt.py", line 165, in main
    display.run_sync()
  File "/Users/marijn/Projects/papermario-jp/diff.py", line 3276, in run_sync
    output, _ = self.run_diff()
                ^^^^^^^^^^^^^^^
  File "/Users/marijn/Projects/papermario-jp/diff_evt.py", line 60, in run_diff
    symbols = parse_symbol_addrs()
              ^^^^^^^^^^^^^^^^^^^^
  File "/Users/marijn/Projects/papermario-jp/tools/update_evts.py", line 53, in parse_symbol_addrs
    ram_addr = int(line[:line.find(";")].split("=")[1].strip(), base=0)
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^
IndexError: list index out of range