Fix memory leaks found by DebugAllocator.

src/main.zig

@@ -8,6 +8,7 @@ pub fn main() !void {
     // std.heap.GeneralPurposeAllocator was renamed to DebugAllocator recently.
     var gpa: std.heap.DebugAllocator(.{}) = .init;
     defer _ = gpa.deinit();
+
     const allocator = gpa.allocator();
 
     var backend = try SDLBackend.initWindow(.{

src/random_document.zig

@@ -85,6 +85,7 @@ fn randomizeObjectProperties(allocator: std.mem.Allocator, doc_size: *const Size
                 y += randFloat(rng, -30, 60);
             }
             const slice = try allocator.dupe(Point2_f, list.items);
+            errdefer allocator.free(slice);
             try obj.setProperty(allocator, .{ .data = .{ .points = slice } });
         },
     }
@@ -99,6 +100,7 @@ pub fn addRandomShapes(doc: *Document, allocator: std.mem.Allocator, rng: std.Ra
     for (0..n_root) |_| {
         if (total_count >= max_total) break;
         var obj = try shape.createObject(allocator, randomShapeKind(rng));
+        defer obj.deinit(allocator);
         try randomizeObjectProperties(allocator, &doc.size, &obj, rng);
         try doc.addObject(allocator, obj);
         total_count += 1;
@@ -116,6 +118,7 @@ pub fn addRandomShapes(doc: *Document, allocator: std.mem.Allocator, rng: std.Ra
         for (0..n_children) |_| {
             if (total_count >= max_total) break;
             var child = try shape.createObject(allocator, randomShapeKind(rng));
+            defer child.deinit(allocator);
             try randomizeObjectProperties(allocator, &doc.size, &child, rng);
             try obj.addChild(allocator, child, &doc.next_object_id);
             total_count += 1;