[Issue 18796] std.algorithm.substitute asserts on empty range

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18796

--- Comment #2 from github-bugzilla at puremagic.com ---
Commit pushed to master at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/d95bc60dadc454cc6143971b14a2fbf4e149cb7b
Fix Issue 18796 - Made substitute with multiple range elements correctly
recognize empty base ranges

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