Revert "Deletion of unnecessary checks before specific function calls"

Accidentally committed two patches under the same commit message.  Both
patches will be added immediately after.

This reverts commit fb6f65a01eca950e2e12a87492268e7d2105aa0b.
Deletion of unnecessary checks before calls of the function "free"

The function "free" is documented in the way that no action shall occur for
a passed null pointer. It is therefore not needed that a function caller
repeats a corresponding check.
http://stackoverflow.com/questions/18775608/free-a-null-pointer-anyway-or-check-first

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Removal of unnecessary checks before a few calls of the C++ delete operator

The C++ delete operator can also handle passed null pointers on its own
without unexpected side effects.
http://www.parashift.com/c++-faq/delete-handles-null.html

It is therefore not needed to keep additional safety checks directly before
such function calls.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>