Use empty string as default value, if variable is null

If ensuers us that there will be no error when we introduce strict_types

Author: michalbundyra

src/Scanner/ClassScanner.php

@@ -913,7 +913,7 @@ protected function scan()
                 $tokenType    = null;
                 $tokenContent = $token;
                 $tokenLine    = $tokenLine + substr_count(
-                    $lastTokenArray[1],
+                    $lastTokenArray[1] ?? '',
                     "\n"
                 ); // adjust token line by last known newline count
             } else {

src/Scanner/MethodScanner.php

@@ -452,7 +452,7 @@ protected function scan()
                 $tokenType    = null;
                 $tokenContent = $token;
                 $tokenLine    = $tokenLine + substr_count(
-                    $lastTokenArray[1] ?? null,
+                    $lastTokenArray[1] ?? '',
                     "\n"
                 ); // adjust token line by last known newline count
             } else {