gnu: r-mixedpower: Improve compatibility with R>=4.2.

Upstream’s fix is incomplete and thus commit
7871447cf5 was insufficient.

* gnu/packages/patches/r-mixedpower-r2power.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/statistics.scm (r-mixedpower)[source]: Use it.

gnu/packages/patches/r-mixedpower-r2power.patch

@@ -0,0 +1,26 @@
+From e882fda905150649aa887c72731144330ca297b5 Mon Sep 17 00:00:00 2001
+From: Lars-Dominik Braun <lars@6xq.net>
+Date: Fri, 28 Oct 2022 09:18:11 +0200
+Subject: [PATCH] Fix R2power with R>=4.2
+
+The previous commit missed this if statement.
+---
+ R/meta_functions.R | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/R/meta_functions.R b/R/meta_functions.R
+index a65f0c1..fb3feba 100644
+--- a/R/meta_functions.R
++++ b/R/meta_functions.R
+@@ -172,7 +172,7 @@ R2power <- function(model, data, fixed_effects, simvar,
+   } # end if databased
+ 
+   # 2. SESOI
+-  suppressWarnings(if (SESOI != F){ # supress warning generated by if statement if SESOI =! F
++  suppressWarnings(if (!is.logical(SESOI)){
+ 
+     # change beta coeficients to SESOI values
+     model@beta <- SESOI
+-- 
+2.37.4
+