lottie: fix trim

The bug caused the trim path to not be applied
when it appeared in a group between different
shapes.

src/loaders/lottie/tvgLottieBuilder.cpp

@@ -871,6 +871,7 @@ void LottieBuilder::updateTrimpath(TVG_UNUSED LottieGroup* parent, LottieObject*
     }
 
     P(ctx->propagator)->strokeTrim(begin, end, trimpath->type == LottieTrimpath::Type::Simultaneous);
+    ctx->merging = nullptr;
 }