[Dotenv] Fixed infinite loop with missing quote followed by quoted value

If there's a quote missing to end a value and in the next line there's again a quoted value Dotenv will run into an infinite loop. An .env file with the following content will result in this error:
```
FOO="foo
BAR="bar"
```
See #34642 for more details.

Dotenv.php

@@ -203,7 +203,10 @@ private function lexValue()
                 $this->cursor += 1 + $len;
             } elseif ('"' === $this->data[$this->cursor]) {
                 $value = '';
-                ++$this->cursor;
+
+                if (++$this->cursor === $this->end) {
+                    throw $this->createFormatException('Missing quote to end the value');
+                }
 
                 while ('"' !== $this->data[$this->cursor] || ('\\' === $this->data[$this->cursor - 1] && '\\' !== $this->data[$this->cursor - 2])) {
                     $value .= $this->data[$this->cursor];

Tests/DotenvTest.php

@@ -40,6 +40,7 @@ public function getEnvDataWithFormatErrors()
             ['FOO', "Missing = in the environment variable declaration in \".env\" at line 1.\n...FOO...\n     ^ line 1 offset 3"],
             ['FOO="foo', "Missing quote to end the value in \".env\" at line 1.\n...FOO=\"foo...\n          ^ line 1 offset 8"],
             ['FOO=\'foo', "Missing quote to end the value in \".env\" at line 1.\n...FOO='foo...\n          ^ line 1 offset 8"],
+            ["FOO=\"foo\nBAR=\"bar\"", "Missing quote to end the value in \".env\" at line 1.\n...FOO=\"foo\\nBAR=\"bar\"...\n                     ^ line 1 offset 18"],
             ['FOO=\'foo'."\n", "Missing quote to end the value in \".env\" at line 1.\n...FOO='foo\\n...\n            ^ line 1 offset 9"],
             ['export FOO', "Unable to unset an environment variable in \".env\" at line 1.\n...export FOO...\n            ^ line 1 offset 10"],
             ['FOO=${FOO', "Unclosed braces on variable expansion in \".env\" at line 1.\n...FOO=\${FOO...\n           ^ line 1 offset 9"],