[analyzer] Fix transitions in check::PreStmt<MemberExpr> checker callback.
[analyzer] Fix transitions in check::PreStmt<MemberExpr> checker callback.

No in-tree checkers use this callback so far, hence no tests. But better fix
this now than remember to fix this when the checkers actually appear.

Patch by Henry Wong!

Differential Revision: https://reviews.llvm.org/D42785


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@324053 91177308-0d34-0410-b5e6-96231b3b80d8

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