Fixed some warnings from Native project

- fastMode assigned twice in ChunkFIle constructor
 - added checking for fail while reading ini file (possible infinity loop)
 - zim_save assigned dithval twice (Please double check this)
 - in http_client added checking progress againt nullptr

ext/native/file/chunk_file.cpp

@@ -8,7 +8,6 @@
 ChunkFile::ChunkFile(const char *filename, bool _read) {
 	data=0;
 	fn = filename;
-	fastMode=false;
 	numLevels=0;
 	read=_read;
 	pos=0;

ext/native/file/ini_file.cpp

@@ -531,7 +531,7 @@ bool IniFile::Load(std::istream &in) {
 	// Maximum number of letters in a line
 	static const int MAX_BYTES = 1024*32;
 
-	while (!in.eof())
+	while (!(in.eof() || in.fail()))
 	{
 		char templine[MAX_BYTES];
 		in.getline(templine, MAX_BYTES);

ext/native/image/zim_save.cpp

@@ -164,7 +164,7 @@ void Convert(const uint8_t *image_data, int width, int height, int pitch, int fl
 				for (int y = 0; y < height; y++) {
 					for (int x = 0; x < width; x++) {
 						int dithval = dith[(x&3)+((y&0x3)<<2)] - 8;
-						dithval = 0;
+						//dithval = 0; please check this
 						int r = clamp32((image_data[i * 4] + dithval/2) >> 3);
 						int g = clamp64((image_data[i * 4 + 1] + dithval/4) >> 2);
 						int b = clamp32((image_data[i * 4 + 2] + dithval/2) >> 3);

ext/native/net/http_client.cpp

@@ -323,6 +323,7 @@ int Client::ReadResponseEntity(Buffer *readbuf, const std::vector<std::string> &
 		bool result = decompress_string(compressed, &decompressed);
 		if (!result) {
 			ELOG("Error decompressing using zlib");
+			if (progress)
 				*progress = 0.0f;
 			return -1;
 		}