LOG_SCOPE_F does not work with fmtlib

I've tried loguru with fmtlib and all seem to work except for LOG_SCOPE_F.

Example 1:
```
LOG_F(INFO, "Test 1: {}", 42);
LOG_F(INFO, "Test 2: {0}", 42);
LOG_F(INFO, "Test 3: {:d}", 42);
```
output
```
2019-11-18 11:55:56.180 loguru_demo.cpp:28 INFO| Test 1: 42
2019-11-18 11:55:56.182 loguru_demo.cpp:29 INFO| Test 2: 42
2019-11-18 11:55:56.185 loguru_demo.cpp:30 INFO| Test 3: 42
```

Example 2:
```
RAW_LOG_F(INFO, "Test 1: {}", 42);
RAW_LOG_F(INFO, "Test 2: {0}", 42);
RAW_LOG_F(INFO, "Test 3: {:d}", 42);
```
output
```
Test 1: 42
Test 2: 42
Test 3: 42
```

Example 3:
```
int a = 0;
CHECK_EQ_F(a, 42, "Expected value {}", 42);
// CHECK_EQ_F(a, 42, "Expected value {0}", 42);
// CHECK_EQ_F(a, 42, "Expected value {:d}", 42);
```
output
`2019-11-18 11:57:39.062 loguru_demo.cpp:37 FATL| CHECK FAILED: a == 42 (0 == 42) Expected value 42
`

Example 4:
```
{
LOG_SCOPE_F(INFO, "Scope 1: {}", 42);
}
{
LOG_SCOPE_F(INFO, "Scope 2: {0}", 42);
}
{
LOG_SCOPE_F(INFO, "Scope 3: {:d}", 42);
}
```
output
```
2019-11-18 11:55:56.189 loguru_demo.cpp:42 INFO| { Scope 1: {}
2019-11-18 11:55:56.191 loguru_demo.cpp:42 INFO| } 0.002 s: Scope 1: {}
2019-11-18 11:55:56.194 loguru_demo.cpp:46 INFO| { Scope 2: {0}
2019-11-18 11:55:56.196 loguru_demo.cpp:46 INFO| } 0.002 s: Scope 2: {0}
2019-11-18 11:55:56.198 loguru_demo.cpp:50 INFO| { Scope 3: {:d}
2019-11-18 11:55:56.201 loguru_demo.cpp:50 INFO| } 0.003 s: Scope 3: {:d}
```

So why is LOG_SCOPE_F not working like the others?