Fix bad file parsing

Author: mantas-done

src/Subtitles.php

@@ -435,6 +435,14 @@ public function loadFromString(string $string, bool $strict = true): self
             }
         }
 
+        foreach ($internal_format as $row) {
+            foreach ($row['lines'] as $line) {
+                if (strlen($line) > 2000) {
+                    throw new UserException('One text line has over 2000 symbols');
+                }
+            }
+        }
+
         $this->internal_format = array_values($internal_format);
         return $this;
     }

tests/OtherTest.php

@@ -143,4 +143,12 @@ public function testNotStrictModeRemovesAllBlocks()
         $actual = (new Subtitles())->loadFromString('00:00:00 01:00:00 help', false)->getInternalFormat();
         $this->assertInternalFormatsEqual([], $actual);
     }
+
+    public function testDoesntAllowLongText()
+    {
+        $this->expectExceptionMessage('One text line has over 2000 symbols');
+
+        $long_text = str_repeat('a', 2001);
+        (new Subtitles())->loadFromString($long_text)->content('srt');
+    }
 }