fix issues found by phpstan

src/Lexer/Lexer.php

@@ -83,15 +83,16 @@ class Lexer
 
 	public function tokenize(string $s): array
 	{
-		if ($this->regexp === null) {
+		if ($this->regexp === null || $this->types === null) {
 			$this->initialize();
 		}
 
+		assert($this->regexp !== null);
+		assert($this->types !== null);
+
 		preg_match_all($this->regexp, $s, $tokens, PREG_SET_ORDER);
 
-		assert($this->types !== null);
 		$count = count($this->types);
-
 		foreach ($tokens as &$match) {
 			for ($i = 1; $i <= $count; $i++) {
 				if ($match[$i] !== null && $match[$i] !== '') {

src/Parser/ParserException.php

@@ -31,9 +31,12 @@ class ParserException extends \Exception
 		$this->currentOffset = $currentOffset;
 		$this->expectedTokenType = $expectedTokenType;
 
+		$json = json_encode($currentTokenValue, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
+		assert($json !== false);
+
 		parent::__construct(sprintf(
 			'Unexpected token %s, expected %s at offset %d',
-			json_encode($currentTokenValue, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES),
+			$json,
 			Lexer::TOKEN_LABELS[$expectedTokenType],
 			$currentOffset
 		));