Gradle plugin shouldn't fail during configuration phase if there's no wire {} block

I applied the plugin:

buildscript {
    dependencies {
        classpath 'com.squareup.wire:wire-gradle-plugin:3.0.2'
    }
}

apply plugin: 'com.squareup.wire'

And immediately after "Import changes" got a configuration failure:

> Invalid path string: "src/main/proto". Path does not exist.

This feels too aggressive. Perhaps the plugin should either:

1. Not fail during configuration if there's no wire {} block in build.gradle.
2. Not fail during configuration at all, only during execution.

Start with the build.gradle configuration shown in the issue and reproduce the failure during Import changes when no wire {} block is present. Inspect the Gradle plugin's configuration-phase handling; done means applying the plugin without that block no longer fails during configuration, though the issue leaves the preferred behavior unresolved.