command/layout: fix a memory leak

 river/command/layout.zig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/river/command/layout.zig b/river/command/layout.zig
index 4ba4f19..e0967c9 100644
--- a/river/command/layout.zig
+++ b/river/command/layout.zig
@@ -33,7 +33,9 @@ pub fn outputLayout(
     if (args.len > 2) return Error.TooManyArguments;
 
     const output = seat.focused_output;
+    const old_layout_namespace = output.layout_namespace;
     output.layout_namespace = try util.gpa.dupe(u8, args[1]);
+    if (old_layout_namespace) |old| util.gpa.free(old);
     output.handleLayoutNamespaceChange();
 }