Fix for broken null call (#177)

Author: brendt

src/Languages/Base/Injections/AdditionInjection.php

@@ -16,7 +16,7 @@
     public function parse(string $content, Highlighter $highlighter): ParsedInjection
     {
         // Standardize line endings
-        $content = preg_replace('/\R/u', PHP_EOL, $content);
+        $content = preg_replace('/\R/u', PHP_EOL, $content) ?? '';
 
         $content = str_replace('❷span class=❹ignore❹❸{+❷/span❸', '{+', $content);
         $content = str_replace('❷span class=❹ignore❹❸+}❷/span❸', '+}', $content);

src/Languages/Base/Injections/DeletionInjection.php

@@ -16,7 +16,7 @@
     public function parse(string $content, Highlighter $highlighter): ParsedInjection
     {
         // Standardize line endings
-        $content = preg_replace('/\R/u', PHP_EOL, $content);
+        $content = preg_replace('/\R/u', PHP_EOL, $content) ?? '';
 
         $content = str_replace('❷span class=❹ignore❹❸{-❷/span❸', '{-', $content);
         $content = str_replace('❷span class=❹ignore❹❸-}❷/span❸', '-}', $content);

src/Languages/Base/Injections/GutterInjection.php

@@ -35,7 +35,7 @@ public function addClass(int $line, string $class): self
 
     public function parse(string $content, Highlighter $highlighter): ParsedInjection
     {
-        $lines = preg_split('/\R/u', trim($content, "\n"));
+        $lines = preg_split('/\R/u', trim($content, "\n")) ?? '';
 
         $gutterNumbers = [];
         $longestGutterNumber = '';

tests/Languages/Base/Injections/AdditionInjectionTest.php

@@ -25,4 +25,14 @@ public function test_addition_injection()
 
         $this->assertSame($expected, Escape::html($parsedInjection->content));
     }
+
+    public function test_null_content_is_prevented(): void
+    {
+        $content = <<<TXT
+{~'_'~}
+TXT;
+        new Highlighter()->parse($content, 'php');
+
+        $this->assertTrue(true);
+    }
 }

tests/targets/test.md

@@ -1,5 +1,3 @@
 ```php
-try {
-} catch (HttpRequestFailed $failure) {
-}
+{~'_'~}
 ```