Fix legacy text conversion filter for UCS-4

If a downstream filter returns -1 (error), the CK macro
will make the UCS-4 conversion filter also immediately
return. This means that any necessary updates to the filter
state have to be done *before* using CK, or it will be left
in an invalid state and will not behave correctly when
flushed.

Author: alexdowad

ext/mbstring/libmbfl/filters/mbfilter_ucs4.c

@@ -191,6 +191,7 @@ int mbfl_filt_conv_ucs4_wchar(int c, mbfl_convert_filter *filter)
 			n = c & 0xff;
 		}
 		n |= filter->cache;
+		filter->status &= ~0xff;
 		if ((n & 0xffff) == 0 && ((n >> 16) & 0xffff) == 0xfffe) {
 			if (endian) {
 				filter->status = 0;		/* big-endian */
@@ -200,7 +201,6 @@ int mbfl_filt_conv_ucs4_wchar(int c, mbfl_convert_filter *filter)
 		} else if (n != 0xfeff) {
 			CK((*filter->output_function)(n, filter->data));
 		}
-		filter->status &= ~0xff;
 		break;
 	}