Fix pasting bailing early when any particle fails to spawn

Broken since 462460b6b3, where the break in the old code was thoughtlessly moved to the new code, the issue being that create_part failing doesn't necessarily mean that we're out of particle IDs. I don't think pasting is a hot enough operation for such optimizations to be necessary, so continue should be fine.

src/simulation/Simulation.cpp

@@ -130,7 +130,7 @@ void Simulation::Load(const GameSave *save, bool includePressure, Vec2<int> bloc
 		auto i = create_part(-3, x, y, tempPart.type);
 		if (i == -1)
 		{
-			break;
+			continue;
 		}
 		if (i > parts.lastActiveIndex)
 		{