throw ParseException when null input is provided

[phil-davis]

Issue #657

parse can be called with input null, but the caller should have previously provided an input stream that is already set up.

The change in this PR makes parse throw a ParseException if it is called the first time with null

This should help anyone calling this, or Reader::read() with no input. Instead of getting a PHP Fatal error, they will get an exception.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.78%. Comparing base (72a1fe9) to head (5d7ca00).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #658   +/-   ##
=========================================
  Coverage     98.78%   98.78%           
- Complexity     1869     1870    +1     
=========================================
  Files            71       71           
  Lines          5254     5256    +2     
=========================================
+ Hits           5190     5192    +2     
  Misses           64       64           

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[alecpl]

The $input parameter is marked as string|resource|null. So, this is a wrong solution.

[alecpl]

I'm sorry, I was confused. The solution looks all right.