UI: Fix changing quick transition to/from fade to black

(cherry picked from commit 35463cb46449aa494a9deb5a2ce48521348abab7)

UI/window-basic-main-transitions.cpp

@@ -1476,6 +1476,7 @@ void OBSBasic::QuickTransitionChange()
 								trIdx);
 		if (tr) {
 			qt->source = tr;
+			qt->fadeToBlack = fadeToBlack;
 			ResetQuickTransitionText(qt);
 		}
 	}