[dask] Fix LTR with empty partition and NCCL error. #11643

Job	Run time
Build libxgboost4j.so with CUDA	6m 41s
Build libxgboost4j.dylib for MacOS (Apple Silicon)	1m 57s
Build libxgboost4j.so targeting glibc 2.17 (arch aarch64, runner linux-arm64-cpu)	1m 41s
Build libxgboost4j.dylib for MacOS (Intel)	3m 15s
Build and test JVM packages (Linux, Scala 2.12)	10m 15s
Build libxgboost4j.so targeting glibc 2.17 (arch x86_64, runner linux-amd64-cpu)	2m 0s
Build and test JVM packages (Linux, Scala 2.13)	4m 56s
Build and test JVM packages (windows-latest)	9m 9s
Build and test JVM packages (macos-13)	12m 7s
Build docs for JVM packages	4m 41s
Test JVM packages with CUDA (Scala 2.12)	5m 59s
Test JVM packages with CUDA (Scala 2.13)	6m 9s
Deploy JVM packages to S3 (cpu)	10s
Deploy JVM packages to S3 (cpu)	9s
Deploy JVM packages to S3 (gpu)	9s
Deploy JVM packages to S3 (gpu)	11s
	1h 9m 29s

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