FIX: write/lines regression

fixes: Oldes/Rebol-issues#2429

Author: Oldes

src/core/p-file.c

@@ -454,7 +454,7 @@ REBINT Mode_Syms[] = {
 		args = Find_Refines(ds, ALL_WRITE_REFS);
 		spec = D_ARG(2); // data (binary, string, or block)
 
-		if (!(IS_BINARY(spec) || IS_STRING(spec))) {
+		if (!(IS_BINARY(spec) || IS_STRING(spec) || (IS_BLOCK(spec) && (args & AM_WRITE_LINES)))) {
 			//Trap1(RE_INVALID_ARG, spec);
 			REB_MOLD mo = {0};
 			Reset_Mold(&mo);

src/tests/units/port-test.r3

@@ -108,10 +108,12 @@ if system/platform = 'Windows [
 		--assert [type: file size: 51732] = query/mode file [type: size:]
 		close file
 
-	--test-- "write/lines - issue/2102"
+	--test-- "write/lines"
 		;@@ https://github.com/Oldes/Rebol-issues/issues/2102
 		write/lines %tmp.txt {a^/}
 		--assert ["a" ""] = read/lines %tmp.txt
+		;@@ https://github.com/Oldes/Rebol-issues/issues/2429
+		--assert "a^/b^/" = read/string write/lines %tmp.txt ["a" "b"]
 		delete %tmp.txt
 
 	--test-- "read/lines - issue/1794"