[10.x] Address Null Parameter Deprecations in UrlGenerator

[aldobarr]

UrlGenerator can currently receive a null value for $path in isValidUrl and extractQueryString which leads to null being passed to preg_match and strpos respectively which is deprecated.

Resolves #51147

[rodrigopedra]

Both methods' docblocks state that they expect a string.

You can see numerous PR trying to account for nulls like this.

If the deprecation notice is triggered by an internal call of those methods, then the call should be fixed, not the implementation to account for unexpected usage.

[aldobarr]

Both methods' docblocks state that they expect a string.

You can see numerous PR trying to account for nulls like this.

If the deprecation notice is triggered by an internal call of those methods, then the call should be fixed, not the implementation to account for unexpected usage.

Updated PR to fix the specific ones I found earlier.