term.ui: fix panic from missing cursor pos response (#24468)

vlib/term/ui/termios_nix.c.v

@@ -168,6 +168,9 @@ fn get_cursor_position() (int, int) {
 		buf[len] = 0
 		s = tos(buf, len)
 	}
+	if s.len == 0 {
+		return -1, -1
+	}
 	a := s[2..].split(';')
 	if a.len != 2 {
 		return -1, -1

vlib/term/ui/termios_nix_test.v

@@ -0,0 +1,63 @@
+module ui
+
+fn test_get_cursor_position_reads_valid_row_column_data() ! {
+	mut pipeset := [0, 0]
+	mut original_stdin_fd := -1
+	unsafe {
+		if C.pipe(&pipeset[0]) == -1 {
+			return error('unable to create pipe: ${C.strerror(C.errno)}')
+		}
+
+		fake_cursor_pos_data := '\033[45;70R'
+		written_bytes := C.write(pipeset[1], fake_cursor_pos_data.str, fake_cursor_pos_data.len)
+		if written_bytes == -1 {
+			C.close(pipeset[0])
+			C.close(pipeset[1])
+			return error('error writing into pipe: ${C.strerror(C.errno)}')
+		}
+
+		C.close(pipeset[1])
+
+		if C.dup2(pipeset[0], C.STDIN_FILENO) == -1 {
+			C.close(pipeset[0])
+			return error('error redirecting stdin with dup2: ${C.strerror(C.errno)}')
+		}
+
+		C.close(pipeset[0])
+
+		cursor_pos_x, cursor_pos_y := get_cursor_position()
+		assert cursor_pos_x == 45
+		assert cursor_pos_y == 70
+	}
+}
+
+fn test_get_cursor_position_reads_empty_position_data() ! {
+	mut pipeset := [0, 0]
+	mut original_stdin_fd := -1
+	unsafe {
+		if C.pipe(&pipeset[0]) == -1 {
+			return error('unable to create pipe: ${C.strerror(C.errno)}')
+		}
+
+		fake_cursor_pos_data := ''
+		written_bytes := C.write(pipeset[1], fake_cursor_pos_data.str, fake_cursor_pos_data.len)
+		if written_bytes == -1 {
+			C.close(pipeset[0])
+			C.close(pipeset[1])
+			return error('error writing into pipe: ${C.strerror(C.errno)}')
+		}
+
+		C.close(pipeset[1])
+
+		if C.dup2(pipeset[0], C.STDIN_FILENO) == -1 {
+			C.close(pipeset[0])
+			return error('error redirecting stdin with dup2: ${C.strerror(C.errno)}')
+		}
+
+		C.close(pipeset[0])
+
+		cursor_pos_x, cursor_pos_y := get_cursor_position()
+		assert cursor_pos_x == -1
+		assert cursor_pos_y == -1
+	}
+}