I20231206-0410
* Prevent NPE in string concat to text block cleanup - add null check for originalVarName field in StringConcatToTextBlockFixCore.visit(ClassInstanceCreation) - fixes: #950 - add new test scenarios to CleanUpTest15
* Prevent NPE in string concat to text block cleanup - add null check for originalVarName field in StringConcatToTextBlockFixCore.visit(ClassInstanceCreation) - fixes: #950 - add new test scenarios to CleanUpTest15