FIX: crash in enline

related to: zsx#16

(cherry picked from commit 11a9478)

Author: Oldes

src/core/s-ops.c

@@ -458,10 +458,11 @@ static REBYTE seed_str[SEED_LEN] = {
 	// Add missing CRs:
 	while (cnt > 0) {
 		bp[tail--] = bp[len]; // Copy src to dst.
-		if (bp[len--] == LF && bp[len] != CR) {
+		if (bp[len] == LF && (len == 0 || bp[len - 1] != CR)) {
 			bp[tail--] = CR;
 			cnt--;
 		}
+		len--;
 	}
 }
 
@@ -495,10 +496,11 @@ static REBYTE seed_str[SEED_LEN] = {
 	// Add missing CRs:
 	while (cnt > 0) {
 		bp[tail--] = bp[len]; // Copy src to dst.
-		if (bp[len--] == LF && bp[len] != CR) {
+		if (bp[len] == LF && (len == 0 || bp[len - 1] != CR)) {
 			bp[tail--] = CR;
 			cnt--;
 		}
+		len--;
 	}
 }
 

src/tests/units/crash-test.r3

@@ -125,6 +125,10 @@ Rebol [
 	;@@ https://github.com/Oldes/Rebol-issues/issues/1514
 	--assert error? try [try/except [1 / 0] :add] ;- no crash
 
+--test-- {enline "^/"}
+	--assert string? enline "^/"  ;- no crash
+	--assert string? enline "^/č" ;- no crash (unicode version)
+
 ===end-group===
 
 ~~~end-file~~~