Fix incremental test (DefaultImpls are not generated for an empty interface)

Author: yanex

jps-plugin/testData/incremental/pureKotlin/traitClassObjectConstantChanged/build.log

@@ -1,14 +1,12 @@
 Cleaning output files:
 out/production/module/test/Trait$Companion.class
-out/production/module/test/Trait$DefaultImpls.class
 out/production/module/test/Trait.class
 End of files
 Compiling files:
 src/const.kt
 End of files
 Cleaning output files:
 out/production/module/test/Trait$Companion.class
-out/production/module/test/Trait$DefaultImpls.class
 out/production/module/test/Trait.class
 out/production/module/test/Usage.class
 End of files