Fix Iter.field for non-owned components

src/iter.zig

@@ -43,7 +43,9 @@ pub fn Iter(comptime ctx: anytype) type {
         pub fn field(self: Self, comptime T: type, index: usize) []T {
             var raw_ptr = c.ecs_field_w_size(self.raw, @sizeOf(T), @intCast(index));
             var typed_ptr: [*]T = @alignCast(@ptrCast(raw_ptr));
-            return typed_ptr[0..self.getCount()];
+            const is_self = c.ecs_field_is_self(self.raw, @intCast(index));
+            const count = if (is_self) self.getCount() else 1;
+            return typed_ptr[0..count];
         }
 
         pub fn fieldId(self: Self, index: usize) Id(ctx) {