Fix crash with loadables in Android. Warn if done() is being called twice.

libs/loadable/loadable.nim

@@ -281,9 +281,14 @@ proc loadUri*(
 
     if not is_remote:
         start_func = proc(self: LoadableResource) =
+            when not defined(release):
+                var done_called = false
             try:
                 var memfile = memfiles.open(uri, mode=fmRead)
                 self.done_func = proc() =
+                    when not defined(release):
+                        assert not done_called, "Done is being called multiple times. Did you forget to set auto_done = false?"
+                        done_called = true
                     memfile.close()
                 self.onload(true, "", memfile.mem, memfile.size)
                 # TODO!!!! check whether these objects are freed

src/loaders/blend.nim

@@ -88,14 +88,9 @@ proc registerBlendLoader*(engine: MyouEngine) =
             e.newBlendLoader()
         )
 
-var used_resources: seq[LoadableResource]
-
 method close*(self: BlendLoader) =
     if self.resource != nil:
         self.resource.done()
-        # TODO: investigate
-        # this is a hack to avoid a crasn on android
-        used_resources.add self.resource
         self.resource = nil
         self.blend_file = nil
         self.cached_materials.clear()
@@ -111,12 +106,16 @@ proc loadAsync(self: BlendLoader, callback: proc()) =
         callback()
     else:
         self.close()
-        self.resource = self.blend_file_path.loadUri proc(ok, err, data, len: auto) =
+        self.resource = loadUri(self.blend_file_path,
+            proc(ok, err, data, len: auto) =
                 if ok:
                     self.blend_file = openBlendFile(self.blend_file_path, data, len)
                     callback()
                 else:
                     raise IOError.newException err
+            ,
+            auto_done = false
+        )
 
 type BlenderObTypes = enum
     BEmpty = 0