Update unzip.c

- Fix compiler warning.

contrib/unzip/unzip.c

@@ -1175,7 +1175,7 @@ extern int ZEXPORT unzOpenCurrentFile3(unzFile file, int *method, int *level, in
             pfile_in_zip_read_info->stream.zalloc = (alloc_func)0;
             pfile_in_zip_read_info->stream.zfree = (free_func)0;
             pfile_in_zip_read_info->stream.opaque = (voidpf)s;
-            pfile_in_zip_read_info->stream.next_in = 0;
+            pfile_in_zip_read_info->stream.next_in = (voidpf)0;
             pfile_in_zip_read_info->stream.avail_in = 0;
 
 #ifdef HAVE_APPLE_COMPRESSION
@@ -1997,4 +1997,4 @@ extern int ZEXPORT unzEndOfFile(unzFile file)
 
 #ifdef _MSC_VER
 #   pragma warning(pop)
-#endif // _MSC_VER
+#endif // _MSC_VER