Add test for fread segfault with \x1a bytes

Reproduces issue #7407 where fread crashes when reading files
with \x1a (ASCII SUB) character. Manual testing confirms both
test cases trigger segmentation fault as expected.

Author: ANAMASGARD

inst/tests/tests.Rraw

@@ -21858,3 +21858,14 @@ test(2344.04, key(DT[, .(V4 = c("b", "a"), V2, V5 = c("y", "x"), V1)]), c("V1",
 
 # fread with quotes and single column #7366
 test(2345, fread('"this_that"\n"2025-01-01 00:00:01"'), data.table(this_that = as.POSIXct("2025-01-01 00:00:01", tz="UTC")))
+
+# Test cases that reproduce the segfault when fread encounters \\x1a (ASCII SUB) character at or near end of field #7407
+test(9063.1, {
+  fread(text=paste0("foo\n", strrep("a", 4096*100), "\x1a"))
+  TRUE
+}, TRUE)
+
+test(9063.2, {
+  fread(text="a,b\n1,2\n3,4\x1a")
+  TRUE
+}, TRUE)