According to the manual, it can be played with the Light Phaser or the Controller, but the controller should be in Port 2.
You can choose, in the Port 1/2 controls sub-menus, to which console port the controllers are mapped. If you map the 1st controller to Port 2 and vice-versa (2nd controller to Port 1), this will enable you to play using the controller, without a light gun device - the game will detect you have the controller in the 2nd port and start without light gun support.
Looks like you've not defined a Hotkey when asked in EmulationStation input mapping - that's why B resets the current game.
What version of RetroPie are you using ? Can you add more info about your setup, as detailed in https://retropie.org.uk/forum/topic/3/read-this-first ?
Thanks - but I don't think it's a Dolphinbar specific issue. I can get it to crash with just a plain old keyboard/mouse switch too.
Doing a bit of debugging work I have found if I comment out this bit of code on line 2489 of libretro.c it no longer crashes. You lose the crosshairs obviously but otherwise it works fine, so it seems that something in the crosshair generating code is related to the crash. At least now I've got an idea of where the crash is originating from, I'll see if I can debug further and once I've got some better idea of the root cause I can post the issue to the core's github repo for further discussion.
Lines 2487 - 2490 on libretro.c
if (input.system == SYSTEM_LIGHTPHASER)
//draw_cursor(input.analog, input.analog, 0x001f);