Fix potential memory leak if zstd_compress fails

This PR fixes a potential memory leak in the compression path.

In the current implementation, if zstd_compress returns an error, rb_raise is called immediately.
If rb_raise will be called, the subsequent ZSTD_freeCCtx(ctx) is never reached.

This change ensures that ZSTD_freeCCtx(ctx) is called before raising the exception, preventing the context leak.
Seems zstd_compress errors are rare in practice, this fix ensures safety for those edge cases.

Author: Watson1978

ext/zstdruby/zstdruby.c

@@ -30,12 +30,12 @@ static VALUE rb_compress(int argc, VALUE *argv, VALUE self)
   char* output_data = RSTRING_PTR(output);
 
   size_t const ret = zstd_compress(ctx, output_data, max_compressed_size, input_data, input_size, false);
+  ZSTD_freeCCtx(ctx);
   if (ZSTD_isError(ret)) {
     rb_raise(rb_eRuntimeError, "compress error error code: %s", ZSTD_getErrorName(ret));
   }
   rb_str_resize(output, ret);
 
-  ZSTD_freeCCtx(ctx);
   return output;
 }