Fix checking valid jpeg file logic

Author: kevyuu

src/nbl/asset/interchange/CImageLoaderJPG.cpp

@@ -157,10 +157,11 @@ bool CImageLoaderJPG::isALoadableFileFormat(system::IFile* _file, const system::
 	if (!_file)
 		return false;
 
-	uint32_t header = 0;	
+	uint16_t soiMarker = 0;	
 	system::IFile::success_t success;
-	_file->read(success, &header, 6, sizeof(uint32_t));
-	return success && ((header&0x00FFD8FFu)==0x00FFD8FFu || header == 0x4a464946 || header == 0x4649464a || header == 0x66697845u || header == 0x70747468u); // maybe 0x4a464946 can go
+	_file->read(success, &soiMarker, 0, sizeof(uint16_t));
+	constexpr auto JPEG_VALID_SOI_MARKER = 0xD8FF;
+	return success && (soiMarker == JPEG_VALID_SOI_MARKER);
 #endif
 }