Issue type:

[ ] question
[x] bug report
[ ] feature request
[ ] documentation issue

Database system/driver:

[ ] cordova
[ ] mongodb
[ ] mssql
[ ] mysql / mariadb
[ ] oracle
[x] postgres
[ ] cockroachdb
[ ] sqlite
[ ] sqljs
[ ] react-native
[ ] expo

TypeORM version:

[x] latest (0.2.18)
[ ] @next
[x] 0.2.18 (or put your version here)

Steps to reproduce or a small repository showing the problem:

For an Entity column like this:

class Thing {
  // ...
  @Column({ type: "hstore", hstoreType: "object" })
  public values: Record<string, string>;
}

The values property is not restored properly when saving & restoring the
entity: Empty string values in the map (EG { foo: "1", bar: ""} cause the object to break.

For clarity & reproduction, I've created an isolated bare-minimum repository that acts as an example of the issue.

See https://github.com/tobyhinloopen/typeorm-failure for a runnable example.