RFR: Fix WinPerfAsmProfiler init exception when Utils.tryWith return Collections.singleton

[XIACYBING]

When Windows Performance Toolkit is not installed in Windows environment, WinPerAsmProfiler will start abnormally and throw wrong message due to wrong operation.

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Commit messages:
 - Fix WinPerfAsmProfiler init exception when Utils.tryWith return Collections.singleton

Changes: https://git.openjdk.java.net/jmh/pull/72/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmh&pr=72&range=00
  Stats: 12 lines in 1 file changed: 8 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jmh/pull/72.diff
  Fetch: git fetch https://git.openjdk.java.net/jmh pull/72/head:pull/72

PR: https://git.openjdk.java.net/jmh/pull/72