Update to AssemblyScript version 0.19.10.
This version breaks compatibility with subgraphs that use older versions of graph-cli, graph-ts and by consequence AssemblyScript.
To upgrade your subgraph follow this guide: https://gist.github.com/otaviopace/8406cb39644d2e7678570d1e7f50dac4.
Once the final version is released, this guide will be moved to the official docs.