[Bug Report] Compiler crashes when compiling all() on iterating over a heterogenouos tuple

### Environment
- Codon version: v0.19.3
- OS: Debian bullseye

### Description
Codon compiler crashes with a segmentation fault when compiling code that uses a generator expression with `all()` to iterate over a tuple of multiple class instances.

### Steps to Reproduce

1. Code

```python
class A:
def __init__(self, a: int):
self.a = a

def filter(self, x: int) -> bool:
return x % self.a == 0

class B:
def __init__(self, b: float):
self.b = b

def filter(self, x: int) -> bool:
return x % self.b == 0

class FilterCombiner:
def __init__(self, *args):
self.filters = tuple(args)

def filter(self, x: int) -> bool:
return all(f.filter(x) for f in self.filters)

fc = FilterCombiner(A(2), B(3.0))
fc.filter(1)
```

2. Run: `./codon run crash_on_filter.py`

### Expected Behavior
The code should compile and execute successfully, returning the result of the filter operation.

### Actual Behavior
The compiler crashes with a segmentation fault:
```
[1] 1803306 segmentation fault (core dumped) ./codon run temp/crash_on_filter.py
```

### Debug Information

Using GDB, the crash occurs at:
```
Program received signal SIGSEGV, Segmentation fault.
codon::ast::TypecheckVisitor::visit (this=0x7fffffff7dd0, expr=0xe2af2f0)
at codon/parser/visitors/typecheck/collections.cpp:144
```

**Stack trace:**
```
#0 codon::ast::TypecheckVisitor::visit (this=0x7fffffff7dd0, expr=0xe2af2f0)
at codon/parser/visitors/typecheck/collections.cpp:144
```

**Root cause location:**
File: `codon/parser/visitors/typecheck/collections.cpp:144`

Function:
```cpp
Expr *GeneratorExpr::getFinalExpr() {
auto s = *(getFinalStmt());
if (cast(s))
return cast(s)->getExpr();
return nullptr;
}
```

**GDB inspection:**
```
(gdb) p expr
$1 = (codon::ast::GeneratorExpr *) 0xe2af2f0

(gdb) p expr->getFinalExpr()
$2 = (codon::ast::Expr *) 0x0
```

The issue appears to be that `getFinalExpr()` returns `nullptr`, which is then dereferenced, causing the segmentation fault.

The crash occurs during type checking of the generator expression `(f.filter(x) for f in self.filters)` when used with `all()`. The `GeneratorExpr::getFinalExpr()` returns null, suggesting the generator expression's final statement is not properly initialized or handled during type checking when dealing with heterogeneous class types (A and B) stored in a tuple.