Fix for skip outside test (#2039)

Fixes #2038

Author: kevinushey

NEWS.md

@@ -1,5 +1,8 @@
 # testthat (development version)
 
+* Fixed an issue where calling `skip()` outside of an active test could
+  cause an unexpected error (@kevinushey, #2039).
+
 # testthat 3.2.2
 
 ## New expectations

R/snapshot-reporter.R

@@ -35,7 +35,9 @@ SnapshotReporter <- R6::R6Class("SnapshotReporter",
     },
 
     start_test = function(context, test) {
-      self$test <- gsub("\n", "", test)
+      if (is.character(test)) {
+        self$test <- gsub("\n", "", test)
+      }
     },
 
     # Called by expectation