Fix deadlock on changing to builtin themes #53

Job	Run time
package-macos (x86-64-macos, x86_64-macos, macos-latest)	1m 41s
package-macos (arm64-macos, aarch64-macos, macos-latest)	6m 10s
package (x86-64-windows, x86_64-windows-msvc, ubuntu-latest)	6m 9s
package (arm64-linux, aarch64-linux-gnu, ubuntu-latest)	6m 7s
package (x86-64-linux, x86_64-linux-gnu, ubuntu-latest)	6m 7s
package (arm64-windows, aarch64-windows-msvc, ubuntu-latest)	6m 8s
assemble	1s
package (x86-64-windows, x86_64-windows-msvc, ubuntu-latest)	14m 5s
package (x86-64-linux, x86_64-linux-gnu, ubuntu-latest)	6m 53s
package (arm64-linux, aarch64-linux-gnu, ubuntu-latest)	11m 21s
package-macos (x86-64-macos, x86_64-macos, macos-latest)	1m 52s
package (arm64-windows, aarch64-windows-msvc, ubuntu-latest)	15m 23s
package-macos (arm64-macos, aarch64-macos, macos-latest)	11m 31s
assemble	0s
package-macos (x86-64-macos, x86_64-macos, macos-latest)	11m 27s
package (arm64-windows, aarch64-windows-msvc, ubuntu-latest)	15m 23s
package (arm64-linux, aarch64-linux-gnu, ubuntu-latest)	11m 21s
package (x86-64-linux, x86_64-linux-gnu, ubuntu-latest)	6m 53s
package-macos (arm64-macos, aarch64-macos, macos-latest)	11m 31s
package (x86-64-windows, x86_64-windows-msvc, ubuntu-latest)	14m 5s
assemble	26s
	2h 44m 34s

Provide feedback