Exit From Gridview.builder Iteration In Flutter Or Remove Empty Space

I am trying to implement a vision board. I'm using gridview.builder for adding up to 12 images. Almost everything works as I expect: adding up to 12 images, but when the limit is reached, somehow I want to stop the iteration, because I am not able to return null, and any widget I return, it will create additional space I don't want.

 GridView.builder(
                clipBehavior: Clip.none,
                physics: ScrollPhysics(),
                shrinkWrap: true,
                gridDelegate: SliverGridDelegateWithMaxCrossAxisExtent(
                    maxCrossAxisExtent: SizeConfig.screenWidth!/3,
                    crossAxisSpacing: 0,
                    mainAxisSpacing: 0),
                itemCount: visions.length+1,
                itemBuilder: (BuildContext ctx, index) {
                  print("__________");
                  print("AM INTRAT IN ITEM BUILDER");
                  print("INDEX $index");
                  print(visions.length);
                  if (index < visions.length) {
                    print("PHOTO ALREADY ADDED CONTAINER");
                    return Stack(
                      alignment: Alignment.center,
                      children: [
                        Container(
                          width: double.infinity,
                          height: double.infinity,
                        ),
                        Container(
                          width: SizeConfig.screenWidth!/4,
                          height: SizeConfig.screenWidth!/4,
                          decoration: BoxDecoration(
                            image: DecorationImage(
                                image: FileImage(File(visions[index])),
                                fit: BoxFit.cover),
                            borderRadius: const BorderRadius.all(
                                Radius.circular(
                                    5.0) //                 <--- border radius here
                            ),
                          ),
                        ),
                        Positioned(
                          top:0,
                          right:0,
                          child: Container(
                            child: ClipOval(
                              child: InkWell(
                                onTap: () {
                                  _removeVisions(index);
                                },
                                child: Container(
                                  padding: const EdgeInsets.all(5),
                                  color: Colors.white,
                                  child:
                                    const Icon(
                                        Icons.delete,
                                        size: 16,
                                        color: Color(0xff221F1E)),
                                ),
                              ),
                            ),
                          ),
                        ),
                      ],
                      clipBehavior: Clip.none,
                    );
                  }
                  else if(index<12){
                    print("ADAUGA POZA");
                    print("INDEX $index");
                    print(visions.length);
                    return InkWell(
                      onTap: () {
                        _openGallery(context);
                      },
                      child:
                      Stack(
                        alignment: Alignment.center,
                        children:[
                          Container(
                          width: SizeConfig.screenWidth!/4,
                            height: SizeConfig.screenWidth!/4,
                            decoration:
                            BoxDecoration(
                              border: Border.all(color: const Color(0xff221F1E)),
                              borderRadius: const BorderRadius.all(Radius.circular(5.0)),
                            ),
                            child:
                              const Icon(
                                Icons.add,
                                size: 22,
                                color: Color(0xff221F1E),
                              )
                        ),
                        ],
                      ),
                    );
                  }
                  else {
                    return  Container(color: Colors.red);
                  }
                }
            ),

I want to remove that red container. I have also tried to hardcode something with Positioned widget, but nothing worked, so I am trying somehow to exit when index is equal to 12 or any other solution...

I would try a true/false statement like this for your itemcount:

itemCount: (visions.length == 12) ? visions.length : visions.length + 1,