Silence a coverity warning about comparing the address of pointer 'ch…

…ild' when it might be null. None issue, but it does no harm to fix.

mythtv/libs/libmythui/mythuitype.cpp

@@ -182,6 +182,9 @@ void MythUIType::DeleteChild(const QString &name)
  */
 void MythUIType::DeleteChild(MythUIType *child)
 {
+    if (!child)
+        return;
+
     QMutableListIterator<MythUIType *> it(m_ChildrenList);
 
     while (it.hasNext())