Clang crashes when constructor initializer list contains a template parameter type

Clang crashes on the following ~~valid~~ invalid C++ code (when assertions are enabled):
```cpp
struct S0 {
S0(int) {}
template
S0(T) : Member(42), T(42) {};
int Member{21};
};

void InstantiateS0() {
S0 S0Instance(67);
}
```

```
Assertion `IdealIndex < NumIdealInits && "initializer not found in initializer list"' failed.
```

The reproducer on Compiler Explorer:
https://godbolt.org/z/xaEWMM5b5

The correct behaviour would be accepting the code, and warning for the wrong initialization order.