Using GroovySpy on class with propertyMissing() results in unexpected MissingMethodException

Describe the bug

when using GroovySpy() with an obkject that has propertyMissing() implemented, attempts to access dynamic properties results in an exception

To Reproduce

package example

import spock.lang.Specification

class TestClass {

  def propertyMissing(String name) {
    return name
  }
}

class TesterSpec extends Specification {

  def 'No Spy'() {
    given: 'an instance'
      TestClass sut = new TestClass()

    expect: 'property to be returned'
      sut.bob == 'bob'
  }

  // This does not work
  def 'Spy'() {
    given: 'a spied instance'
      TestClass sut = GroovySpy()

    expect: 'property to be returned'
      sut.bob == 'bob'
  }
}

Expected behavior

Both test should pass

Actual behavior

second test fails with

ondition failed with Exception:

sut.bob == 'bob'
|   |
|   groovy.lang.MissingMethodException: No signature of method: example.TestClass.getBob() is applicable for argument types: () values: []
|   Possible solutions: getAt(java.lang.String), getClass(), notify(), every(), grep()
|   	at example.TesterSpec.Spy(TesterSpec.groovy:27)
example.TestClass$$EnhancerByCGLIB$$9a1d9323@7e0f56d8

Java version

Corretto-11

Buildtool version

------------------------------------------------------------
Gradle 6.7
------------------------------------------------------------

Build time:   2020-10-14 16:13:12 UTC
Revision:     312ba9e0f4f8a02d01854d1ed743b79ed996dfd3

Kotlin:       1.3.72
Groovy:       2.5.12
Ant:          Apache Ant(TM) version 1.10.8 compiled on May 10 2020
JVM:          11.0.14.1 (Amazon.com Inc. 11.0.14.1+10-LTS)
OS:           Mac OS X 13.6 x86_64

What operating system are you using

Mac

Dependencies

Using Spock 1.3-groovy-2.4 with Groovy 2.4.12

Additional context

This is in a very specific setup, so on old version of spock/Groovy but I am told it is recreatable with latest version

Start by running the provided TesterSpec and compare the passing “No Spy” example with the failing “Spy” example. Trace GroovySpy handling of the dynamic property access and propertyMissing(String name), using the reported MissingMethodException as the failure point. Done means both examples pass without the exception on a supported Spock/Groovy setup.