Project compiles but engine crashes while clicking on play

The project compiles normally, however when opening the editor and clicking on “play” the engine crashes and shows this error…
Exception thrown at 0x00007FF97F42D93F (UE4Editor-Engine.dll) in UE4Editor.exe: 0xC0000005: Access violation reading location 0x0000000000000340. occurred.

At the bottom left of your screenshot it looks like “ActorThatOpens” is null. You’re passing a pointer around without checking whether it’s null.