Two fixes in RandomStringUtils.random(int, int, int, boolean, boolean, char[], Random)

[garydgregory]

Two fixes in RandomStringUtils.random(int, int, int, boolean, boolean, char[], Random)

• A custom chars array throws IllegalArgumentException because validation loops treat the loop index as a char code point instead of an index into the chars array.
• random() hangs when the specified [start, end) range contains ONLY rejected code points (UNASSIGNED, PRIVATE_USE, SURROGATE). The loop increments count and retries indefinitely.

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