lib/path: properly handle /. in hasStorePathPrefix

lib/path/default.nix

@@ -165,7 +165,7 @@ let
     # This is a workaround for https://github.com/NixOS/nix/issues/12361 which
     # was needed during the experimental phase of ca-derivations and should be
     # removed once the issue has been resolved.
-    || match "[0-9a-z]{52}" (head components) != null;
+    || components != [ ] && match "[0-9a-z]{52}" (head components) != null;
 
 in
 # No rec! Add dependencies on this file at the top.

lib/path/tests/unit.nix

@@ -110,6 +110,12 @@ let
       expected = false;
     };
 
+    # Root path (empty path components list)
+    testHasStorePathPrefixRoot = {
+      expr = hasStorePathPrefix /.;
+      expected = false;
+    };
+
     testHasStorePathPrefixExample1 = {
       expr = hasStorePathPrefix (storeDirPath + "/nvl9ic0pj1fpyln3zaqrf4cclbqdfn1j-foo/bar/baz");
       expected = true;