Fix TypeError when a JSON file can not be read (#10818)

phpstan/baseline.neon

@@ -4365,11 +4365,6 @@ parameters:
 			count: 1
 			path: ../src/Composer/Json/JsonFile.php
 
-		-
-			message: "#^Parameter \\#1 \\$json of static method Composer\\\\Json\\\\JsonFile\\:\\:parseJson\\(\\) expects string\\|null, string\\|false\\|null given\\.$#"
-			count: 1
-			path: ../src/Composer/Json/JsonFile.php
-
 		-
 			message: "#^Parameter \\#1 \\$json of static method Composer\\\\Json\\\\JsonFile\\:\\:validateSyntax\\(\\) expects string, string\\|false given\\.$#"
 			count: 1

src/Composer/Json/JsonFile.php

@@ -110,6 +110,10 @@ class JsonFile
             throw new \RuntimeException('Could not read '.$this->path."\n\n".$e->getMessage());
         }
 
+        if ($json === false) {
+            throw new \RuntimeException('Could not read '.$this->path);
+        }
+
         return static::parseJson($json, $this->path);
     }