The datafusion-cli panics when `union` 2 table with different number of columns.

[HaoYang670]

Describe the bug
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To Reproduce
Steps to reproduce the behavior:

DataFusion CLI v12.0.0
❯ create table t as select 1 as a, 2 as b;
0 rows in set. Query took 0.015 seconds.
❯ select a from t
union
select a as a1, a as a2 from t;
thread 'main' panicked at 'index out of bounds: the len is 1 but the index is 1', datafusion/common/src/dfschema.rs:161:10
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Expected behavior
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We should return a Result will more precise error message

Additional context
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