Ensure pyGUIControlListBox::GetElementW can't attempt to return a null pointer as a std::wstring

(cherry picked from commit 2f1bb87056)

Sources/Plasma/FeatureLib/pfPython/pyGUIControlListBox.cpp

@@ -587,16 +587,17 @@ std::wstring pyGUIControlListBox::GetElementW( UInt16 idx )
 				{
 					// if its a text element type then it should be safe to cast it to a pfGUIListText
 					pfGUIListText* letext = (pfGUIListText*)le;
-					return letext->GetText();
+					return (letext->GetText() != nullptr) ? letext->GetText() : L"";
 				}
 				else if ( le->GetType() == pfGUIListElement::kTreeRoot )
 				{
 					pfGUIListTreeRoot* elroot = (pfGUIListTreeRoot*)le;
-					return elroot->GetTitle();
+					return (elroot->GetTitle() != nullptr) ? elroot->GetTitle() : L"";
 				}
 			}
 		}
 	}
+
 	return L"";
 }