RFR: 8273435: Remove redundant zero-length check in ClassDesc.of

[Andrey Turbanov]

After [JDK-8215510](https://bugs.openjdk.java.net/browse/JDK-8215510) (eed3a536c0) this condition is always `false`. Empty package name is handled separately.
Found by IntelliJ inspection.

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Commit messages:
 - [PATCH] Remove redundant zero-length check in ClassDesc.of

Changes: https://git.openjdk.java.net/jdk/pull/5157/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5157&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273435
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5157.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5157/head:pull/5157

PR: https://git.openjdk.java.net/jdk/pull/5157