Return a defanged version of an IP address where every period '.' is replaced with '[.]'. Return null for null input and an empty string for empty input.

Examples:

Input: address = '1.1.1.1' Output: '1[.]1[.]1[.]1' Explanation: Each period is replaced with [.] Input: address = '255.100.50.0' Output: '255[.]100[.]50[.]0' Explanation: Each period is replaced with [.] Input: address = '192.168.0.1' Output: '192[.]168[.]0[.]1' Explanation: Each period is replaced with [.] Input: address = null Output: null Explanation: Null input returns null Input: address = '' Output: '' Explanation: Empty string returns empty string
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