Lin Mu making the Spatial Storage tool for Ashy had improved his Spatial Skills due to their constant usage. Not only had his control gotten finer, he could now tolerate the erosion of his skill too.
This was something that had been a problem back in the Bridge Plane as the Withering Energy could affect the restraints set by Meld too.
But now, even though the skill was actively being degraded by the Withering energy, Lin Mu was simply supplying more Qi to sustain it. The reason why the skill was disrupted before wasn't the fact that Lin Mu didn't have enough Qi, but that maintaining the skill needed a high output of it which when hampered enough could cause a cascading effect that made the skill deactivate as well as harm the user.
This was why Withering Energy and the Withering Dao were so dangerous, sometimes even more so than the Death Qi.