[prism/compiler] end_cursor should never be NULL

This fixes a failed assertion reported to SimpleCov

https://github.com/simplecov-ruby/simplecov/issues/1113

This can be repro'd as follows:

1. Create a file `test.rb` containing the following code

```
@foo&.(@bar)
```

2. require it with branch coverage enabled

```
ruby -rcoverage -e "Coverage.start(branches: true); require_relative 'test.rb'"
```

The assertion is failing because the Prism compiler is incorrectly
detecting the start and end cursor position of the call site for the
implicit call .()

This patch replicates the parse.y behaviour of setting the default
end_cursor to be the final closing location of the call node.

This behaviour can be verified against `parse.y` by modifying the test
command as follows:

```
ruby --parser=parse.y -rcoverage -e "Coverage.start(branches: true); require_relative 'test.rb'"
```

[Bug #20866]

1 files changed, 4 insertions, 0 deletions

diff --git a/test/coverage/test_coverage.rb b/test/coverage/test_coverage.rb
index 814b7e088b..9db1f8f253 100644
--- a/test/coverage/test_coverage.rb
+++ b/test/coverage/test_coverage.rb
@@ -463,6 +463,8 @@ class TestCoverage < Test::Unit::TestCase
         [:"&.", 3, 7, 0, 7,  6] => {[:then,  4, 7, 0, 7,  6]=>0, [:else,  5, 7, 0, 7,  6]=>1},
         [:"&.", 6, 8, 0, 8, 10] => {[:then,  7, 8, 0, 8, 10]=>1, [:else,  8, 8, 0, 8, 10]=>0},
         [:"&.", 9, 9, 0, 9, 10] => {[:then, 10, 9, 0, 9, 10]=>0, [:else, 11, 9, 0, 9, 10]=>1},
+        [:"&.", 12, 10, 0, 10, 6] => {[:then, 13, 10, 0, 10, 6] => 0, [:else, 14, 10, 0, 10, 6] => 1},
+        [:"&.", 15, 11, 0, 11, 5] => {[:then, 16, 11, 0, 11, 5] => 0, [:else, 17, 11, 0, 11, 5] => 1},
       }
     }
     assert_coverage(<<~"end;", { branches: true }, result)
@@ -475,6 +477,8 @@ class TestCoverage < Test::Unit::TestCase
       b&.foo
       c&.foo = 1
       d&.foo = 1
+      d&.(b)
+      d&.()
     end;
   end