If an operand version specified in an Infinispan CR is removed from the INFINISPAN_OPERAND_VERSIONS json in a subsequent Operator release, then this will result in the Infinispan CR being ignored by the Operator and the following being logged:

"unable to continue reconcilliation. Operand spec.version='%s' is not supported by this Operator version"

If the user then tries to update spec.version to use a supported version, this code will throw a nil pointer dereference error as the version specified in the .status.operand.version is now unknown.

We should update the code so that the upgrade is able to proceed if an unknown version is specified in the .status.operand.version field