Coverity ID 1477438: explicitly ignore zip_source_seek() result in error handling.

lib/zip_source_window.c

diff --git a/lib/zip_source_window.c b/lib/zip_source_window.c
index 72e001e..6129785 100644
--- a/lib/zip_source_window.c
+++ b/lib/zip_source_window.c
@@ -251,7 +251,7 @@
                 }
                 if ((zip_uint64_t)new_offset < ctx->start) {
                     zip_error_set(&ctx->error, ZIP_ER_INVAL, 0);
-                    zip_source_seek(src, (zip_int64_t)ctx->offset, SEEK_SET);
+                    (void)zip_source_seek(src, (zip_int64_t)ctx->offset, SEEK_SET);
                     return -1;
                 }
                 ctx->offset = (zip_uint64_t)new_offset;