Add type validation before explode value

[2646298]

Issue example

In openapi.yml documentation:

parameters:
  name: parameterName
  in: query
  explode: false
  schema:
    type: array
    items:
      type: string

In this case, the parameter is expected to be in the following format:

https://example.com/api/endpoint?parameterName=value1,value2,value3

However, if an invalid request is made like this:

https://example.com/api/endpoint?parameterName[]=value1&parameterName[]=value2

then $value = explode(self::STYLE_DELIMITER_MAP[$this->style], $value); will try to explode array and in PHP 8 throws fatal error: Fatal error: Uncaught TypeError: explode(): Argument #2 ($string) must be of type string, array given

Fix

Check that $value is a string before explode().