empty_count false positive on hex values

[alejandro-isaza]

New Issue Checklist

• Updated SwiftLint to the latest version
• I searched for existing GitHub issues

Describe the bug

The following code causes a empty_count false positive:

if result.count <= 0xff {
    ...
}

Complete output when running SwiftLint, including the stack trace and command used

$ swiftlint lint
abc.swift:115:30: error: Empty Count Violation: Prefer checking `isEmpty` over comparing `count` to zero. (empty_count)

Environment

• SwiftLint version: 0.27.0

• Installation method used: Homebrew

• Which Xcode version: Xcode 10

• Sample: echo "if result.count <= 0xff {}" | swiftlint lint --no-cache --use-stdin --enable-all-rules

// This triggers a violation:
if result.count <= 0xff {
    ...
}