exec: fix valgrind warning on close(-1)

When executing "exec.test" under valgrind, it reports several
warning messages
	Warning: invalid file descriptor -1 in syscall close()

Add proper check around close()

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/jim-exec.c b/jim-exec.c
index 67d2f18..8059a0b 100644
--- a/jim-exec.c
+++ b/jim-exec.c
@@ -1066,10 +1066,10 @@ badargs:
                 close(errorId);
             }
             /* Close parent-only file descriptors */
-            if (outPipePtr) {
+            if (outPipePtr && *outPipePtr != -1) {
                 close(*outPipePtr);
             }
-            if (errFilePtr) {
+            if (errFilePtr && *errFilePtr != -1) {
                 close(*errFilePtr);
             }
             if (pipeIds[0] != -1) {