Swift4 minor fix

[isimple4]

It mainly fixes couple of warnings and errors. Travis-CI should build successfully now.

Checklist

• [ ] New Extension
• [ ] New Test
• [x] Changed more than one extension, but all changes are related
• [x] Trivial change (doesn't require changelog)

[EZSwiftExtensionsBot]

	1 Error
:no_entry_sign:	Please, modify only one extension per pull request.

	3 Messages
:book:	Executed 202 tests, with 0 failures (0 unexpected) in 5.166 (5.505) seconds
:book:	Executed 187 tests, with 0 failures (0 unexpected) in 4.323 (4.510) seconds
:book:	Executed 124 tests, with 0 failures (0 unexpected) in 3.920 (4.027) seconds

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