FIX: Memory corruption when used append/part to binary with char! argument

related to: Oldes/Rebol-issues#2683

Author: Oldes

src/core/f-modify.c

@@ -143,7 +143,7 @@
 		}
 		else if (IS_CHAR(src_val)) {
 			src_ser = BUF_SCAN;
-			src_ser->tail = Encode_UTF8_Char(BIN_HEAD(src_ser), VAL_CHAR(src_val));
+			src_ser->tail = dst_len = Encode_UTF8_Char(BIN_HEAD(src_ser), VAL_CHAR(src_val));
 		}
 		else if (ANY_STR(src_val)) {
 			if (action != A_CHANGE && GET_FLAG(flags, AN_PART)) {

src/tests/units/series-test.r3

@@ -790,6 +790,9 @@ Rebol [
 	--test-- "APPEND binary! char!"
 		--assert #{0001}     = append #{00} #"^(01)"
 		--assert #{00E28690} = append #{00} #"^(2190)"
+		;@@ https://github.com/Oldes/Rebol-issues/issues/2683
+		--assert #{0001}     = append/part #{00} #"^(01)" 10
+		--assert #{00E28690} = append/part #{00} #"^(2190)" 10
 	--test-- "APPEND/part binary!"
 		--assert #{01} = append/part #{} #{0102} 1
 		--assert #{01} = append/part #{} "^(01)^(02)" 1