调试断言失败。nullptr

Question

我开始编程了，我正在使用Visual Studio。我有一个简单的程序，几天前还可以工作，但在使用另一个项目后，它返回给我一个错误：

#define _CRT_SECURE_NO_DEPRECATE
#include <stdio.h>
#include <math.h>

int main() {
    double a = 3;
    FILE *A;

    scanf("%lf", &a);

    A = fopen("B:\\Mis Documentos\\Coding\\Test 200.txt", "wt");
    fprintf(A, "Hello World, I have %lf", a);
    fclose(A);

}

但是我不能编译它，它返回给我this error。这是日志：

'Project1.exe' (Win32): Loaded 'B:\Mis Documentos\Documents\Visual Studio 2015\Projects\Project1\Debug\Project1.exe'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\ntdll.dll'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\kernel32.dll'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\KernelBase.dll'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\vcruntime140d.dll'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\ucrtbased.dll'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-timezone-l1-1-0.dll'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-file-l2-1-0.dll'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-localization-l1-2-0.dll'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-synch-l1-2-0.dll'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-processthreads-l1-1-1.dll'. Symbols loaded.
'Project1.exe' (Win32): Loaded 'C:\Windows\System32\api-ms-win-core-file-l1-2-0.dll'. Symbols loaded.
Debug Assertion Failed!

Program: ...ments\Visual Studio 2015\Projects\Project1\Debug\Project1.exe
File: minkernel\crts\ucrt\src\appcrt\stdio\output.cpp
Line: 31

Expression: stream != nullptr

For information on how your program can cause an assertion failure, see the Visual C++ documentation on asserts.