Errors corrected in CYPEGAS

If, in the list of "Pipes" that can be seen in the " Design and check options to be carried out" (which appears by selecting the “General options” in the "Project" section of the top toolbar) only one pipe could be seen, it could not be introduced in the project. Users had to define more than one, even only one was going to be used in the project. In the 2019.c version, one pipe can be introduced even if only that type is present in the mentioned pipes list.