C Win32: Window Automatically closes

I wanted to create a Word 'corrupter' which actually justs replaces some letters with some ascii alphabet. However, when the 'Generate' button is pressed, the window automatically closes

static HANDLE ghInstance;

HWND hwndEDIT;
int index[10];

static INT_PTR CALLBACK MainDlgProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
        case WM_INITDIALOG:
        {
            hwndEDIT = GetWindow(hwndDlg, IDC_EDIT);

            return TRUE;
        }

        case WM_SIZE:
            /*
             * TODO: Add code to process resizing, when needed.
             */
            return TRUE;

        case WM_COMMAND:
            switch (GET_WM_COMMAND_ID(wParam, lParam))
            {
                case IDC_GENERATE:
                {
                    char input[1000];
                    char output[1000][10];

                    int i, strLength, m, map;
                    int rNmb;
                    int chance;

                    GetWindowText(hwndEDIT, input, 1000);

                    srand(time(NULL));

                    strLength = strlen(input);

                    for(m=0;m<10;m++)
                    {
                        map = 0;
                        strcpy(output[m], input);
                        for(i=0;i<strLength;i++)
                        {
                            switch(output[m][i])
                            {
                                case '\0':
                                    continue;

                                case '\n':
                                    continue;

                                case ' ':
                                    continue;
                            }

                            chance = rand() % 100;

                            if(chance < 25)
                            {
                                rNmb = (rand() % 128) + 128;

                                output[m][i] = rNmb;
                            }
                        }
                        index[m] = SendDlgItemMessage(hwndDlg , IDC_LISTBOX, LB_ADDSTRING, 0, (LPARAM)output[m]);

                        map++;
                        SendDlgItemMessage(hwndDlg, IDC_LISTBOX, LB_SETITEMDATA, (WPARAM)index[m], (LPARAM)map);
                    }
                }
                case IDC_CLOSE:
                    EndDialog(hwndDlg, TRUE);
                    return TRUE;
            }
            break;

        case WM_CLOSE:
            EndDialog(hwndDlg, 0);
            return TRUE;

        /*
         * TODO: Add more messages, when needed.
         */
    }

    return FALSE;
}

I do not see any link between the generate button and the close command