Fix replacement of NA sub-strings in blocking variable #1161

Job	Run time
24.04.2 \| test \| docker	6m 51s
24.04.2 \| test \| docker	6m 51s
24.04.2 \| nogtf \| docker	6m 20s
24.04.2 \| nogtf \| docker	6m 20s
24.04.2 \| affy \| docker	8m 29s
24.04.2 \| affy \| docker	8m 31s
24.04.2 \| maxquant \| docker	6m 21s
24.04.2 \| maxquant \| docker	6m 21s
24.04.2 \| soft \| docker	8m 16s
24.04.2 \| soft \| docker	8m 16s
24.04.2 \| rnaseq_limma \| docker	8m 26s
24.04.2 \| rnaseq_limma \| docker	8m 26s
latest-everything \| test \| docker	6m 36s
latest-everything \| test \| docker	6m 36s
latest-everything \| nogtf \| docker	5m 36s
latest-everything \| nogtf \| docker	5m 36s
latest-everything \| affy \| docker	8m 21s
latest-everything \| affy \| docker	8m 21s
latest-everything \| maxquant \| docker	6m 43s
latest-everything \| maxquant \| docker	6m 43s
latest-everything \| soft \| docker	9m 14s
latest-everything \| soft \| docker	9m 14s
latest-everything \| rnaseq_limma \| docker	7m 6s
latest-everything \| rnaseq_limma \| docker	7m 6s
	2h 56m 40s

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