ERR: Fix GH13139: better error message on invalid pd.eval and df.query input
- [x] closes #13139 
- [x] tests added / passed
- [x] passes `git diff upstream/master | flake8 --diff`
- [x] whatsnew entry

Added test case to check for invalid input(empy string) on pd.eval('') and df.query('').
Used existing helper function(_check_expression) 

## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/14473?src=pr) is 85.26% (diff: 100%)

> Merging [#14473](https://codecov.io/gh/pandas-dev/pandas/pull/14473?src=pr) into [master](https://codecov.io/gh/pandas-dev/pandas/branch/master?src=pr) will increase coverage by **<.01%**

``` diff
@@             master     #14473   diff @@
==========================================
  Files           140        140          
  Lines         50640      50641     +1   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          43175      43178     +3   
+ Misses         7465       7463     -2   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [170d13a...9a5c55f](https://codecov.io/gh/pandas-dev/pandas/compare/170d13ae3b41cb4793554237fdf3ffc0d60aec1d...9a5c55fa8d66e342f04dd57e00116d89dcd4a51a?src=pr)
 just a doc-comment. pls push ; ping when green.
 thanks!
