Adjust number of error markers emitted for truncated ISO-2022-JP escape sequence

Fuzzing revealed a small difference between the number of error
markers which the legacy ISO-2022-JP and JIS7/8 conversion code
emitted for truncated escape sequences and those emitted by the
new code. The behavior of the old code seems more reasonable
here, so we will imitate it.

Author: alexdowad

ext/mbstring/libmbfl/filters/mbfilter_jis.c

@@ -480,6 +480,8 @@ static size_t mb_iso2022jp_to_wchar(unsigned char **in, size_t *in_len, uint32_t
 			/* ESC seen; this is an escape sequence */
 			if ((e - p) < 2) {
 				*out++ = MBFL_BAD_INPUT;
+				if (p != e && (*p == '$' || *p == '('))
+					p++;
 				continue;
 			}
 

ext/mbstring/tests/iso2022jp_encoding.phpt

@@ -196,6 +196,13 @@ for ($i = 0; $i <= 0xFF; $i++) {
 identifyInvalidString("\x1B", 'JIS');
 identifyInvalidString("\x1B", 'ISO-2022-JP');
 
+convertInvalidString("\x1B$", "%", "JIS", "UTF-8");
+convertInvalidString("\x1B$", "%", "ISO-2022-JP", "UTF-8");
+convertInvalidString("\x1B(", "%", "JIS", "UTF-8");
+convertInvalidString("\x1B(", "%", "ISO-2022-JP", "UTF-8");
+convertInvalidString("\x1B,", "%,", "JIS", "UTF-8");
+convertInvalidString("\x1B,", "%,", "ISO-2022-JP", "UTF-8");
+
 echo "All escape sequences work as expected\n";
 
 foreach (['JIS', 'ISO-2022-JP'] as $encoding) {