RFR: 8292625: jshell crash on "var a = a"

[Bo Zhang]

This commit adds the missing `type` assignment after attributing a variable's initial value. In some cases, this issue causes an NPE.

This issue has existed for a long time, but the NPE was swallowed until https://github.com/openjdk/jdk/commit/433394203dce55db95caefcb57bac9ec114ebc47 stopped swallowing such exceptions.

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Commit messages:
 - 8292625: jshell crash on "var a = a"

Changes: https://git.openjdk.org/jdk/pull/11263/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11263&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292625
  Stats: 13 lines in 2 files changed: 11 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/11263.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11263/head:pull/11263

PR: https://git.openjdk.org/jdk/pull/11263