Invalid syntax is not properly handled.

[ytoml]

Describe the bug
When some tokens are passed without operator (thus Invalid Syntax), compiler trys to report error upsets.

Reproducible code
Just writing literals without operators in a row:

>>> 1 2 3

produces:

Error[#0000]: File <stdin>
?│ 1 2 3

CompilerSystemError: the number of elements in the stack is invalid (num of elems: 3, block id: 1)
this is a bug of the Erg compiler, please report it (https://github.com/erg-lang/erg)
caused from: erg_compiler::codegen::CodeGenerator::codegen
Traceback (most recent call last):
  File "<string>", line 17, in <module>
ConnectionResetError: [Errno 54] Connection reset by peer

Expected behavior
Expected that REPL just reports Invalid Syntax Error.

[ytoml]

I also found that it could accept invalid statement:

Erg interpreter 0.2.8 (tags/?:, 2022/08/25 23:56:48) on aarch64/macos
>>> x = 1 2

And with these inputs(just x, twice) after above, REPL server suddenly shuts down without meaningful messages:

>>> x

>>> x
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 32, kind: BrokenPipe, message: "Broken pipe" }', /Users/ytomida/.cargo/registry/src/jackfan.us.kg-1ecc6299db9ec823/erg-0.2.8/src/dummy.rs:69:49
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[mtshiba]

These codes are actually syntactically acceptable; the call syntax in Erg is of the form call := callable method_name? args, and any object callable that implements Callable trait can be called (this is a specification inherited from Python).
Of course, Int is not Callable, so the type checker should cause an error, but it is crashing, so that is the problem.

[mtshiba]

It is still as strange as ever, but it is no longer a crash.

>>> 1 2
2
>>> x = 1 2
2
>>> 1 2 3
3

[mtshiba]

This has become a parsing issue, so this issue is closed.
Please see here for the rest of the issue.

#95