RegExp: Avoid possible segfault

alib2data/src/regexp/formal/FormalRegExpConcatenation.cpp

@@ -93,7 +93,7 @@ void FormalRegExpConcatenation::setRightElement(const FormalRegExpElement& eleme
 	FormalRegExpElement* elem = element.clone();
 	if(this->parentRegExp && !elem->attachRegExp(this->parentRegExp))
 		throw exception::AlibException("Input symbols not in the alphabet.");
-	delete left;
+	delete right;
 	this->right = elem;
 }
@@ -101,7 +101,7 @@ void FormalRegExpConcatenation::setRightElement(FormalRegExpElement&& element) {
 	FormalRegExpElement* elem = std::move(element).plunder();
 	if(this->parentRegExp && !elem->attachRegExp(this->parentRegExp))
 		throw exception::AlibException("Input symbols not in the alphabet.");
-	delete left;
+	delete right;
 	this->right = elem;
 }