Segmentation Fault in Double-chained Lists

I have a problem with the implementation of double-chained lists, my code is as follows:

#include <stdio.h>
#include <stdlib.h>
struct MoveList
{
    int curRow, curCol, newRow, newCol, isEat;
    struct MoveList *next, *prev;
};

struct MoveList *getNewNode(int cRow, int cCol, int nRow, int nCol, int isEat)
{
    struct MoveList *newNode = (struct MoveList *)malloc(sizeof(struct MoveList));
    newNode->curCol = cCol;
    newNode->curRow = cRow;
    newNode->newCol = nCol;
    newNode->newRow = nRow;
    newNode->isEat = isEat;
    newNode->prev = NULL;
    newNode->next = NULL;
    return newNode;
};

struct MoveList *inserir(int cRow, int cCol, int nRow, int nCol, int isEat, struct MoveList *lista)
{
    struct MoveList *newNode = getNewNode(cRow, cCol, nRow, nCol, isEat);

    if(lista == NULL) return newNode;

    newNode->prev = lista;
    lista->next = newNode;
    return newNode;
}

struct MoveList *merge(struct MoveList *l1, struct MoveList *l2)
{
    if(l1 == NULL && l2 == NULL) return NULL;
    if(l1 == NULL) return l2;
    if(l2 == NULL) return l1;

    struct MoveList *tmp1 = l1, *tmp2 = l2;

    while(tmp1->next != NULL) tmp1 = tmp1->next;
    while(tmp2->prev != NULL) tmp2 = tmp2->prev;

    tmp1->next = tmp2;
    tmp2->prev = tmp1;

    while(tmp1->next != NULL) tmp1 = tmp1->next;

    return tmp1;
}

void imprimir(struct MoveList *lista)
{
    struct MoveList *temp = lista;

    if(temp == NULL) return;

    while(temp->prev != NULL) temp = temp->prev;

    while(temp!=NULL)
    {
        printf("%d:%d -> %d:%d\n", temp->curRow, temp->curCol, temp->newRow, temp->newCol);
        temp = temp->next;
    }
}

int main()
{
    struct MoveList *l1, *l2;
    int x;
    for(x=0;x<5;x++)
    {
        l1 = inserir(x,x,x+1,x+1,0,l1);
        l2 = inserir(x,x,x+1,x+1,0,l2);
    }
    imprimir(l1);
}

The error gives the line "while (temp-> temp! = NULL) temp = temp-> prev;" within the print function.

If I comment the line "l2 = insert (x, x, x + 1, x + 1.0, l2);" inside the main function, the code works.

Someone can help me to solve this problem, grateful already.