code: public static void checkIsSetGlobal(final DelegateExecution execution, final String variableName) {
      Preconditions.checkArgument(variableName != null, VARIABLE_SKIP_GUARDS);
  
      final Object variable = execution.getVariable(variableName);
      Preconditions.checkState(variable != null,
          String.format("Condition of task '%s' is violated: Global variable '%s' is not set.", new Object[] { execution.getCurrentActivityId(), variableName }));
    }
docs: Checks, if a global variable with specified name is set.
  
  @param execution
  process execution.
  @param variableName
  name of the variable to check.