epan: Check for valid cf->edt before free.

Added a check for a valid cf->edt before calling epan_dissect_free(),
as this will give an unintended assert.

This is related to da71ccbf778cca5d9c48e010597570a40fd190c0.

Change-Id: I7f7ceb1b25cfa2400063947f674df10ed6a93e9d
Reviewed-on: https://code.wireshark.org/review/11934
Reviewed-by: Stig Bjørlykke <stig@bjorlykke.org>
(cherry picked from commit 8c211d51ef66b64c708f7ad079e7e7e913ac9f14)
Reviewed-on: https://code.wireshark.org/review/11935

1 files changed, 4 insertions, 2 deletions

diff --git a/file.c b/file.c
index 06134f22a9..84f1db12e5 100644
--- a/file.c
+++ b/file.c
@@ -1631,8 +1631,10 @@ rescan_packets(capture_file *cf, const char *action, const char *action_item, gb
     cf->redissecting = TRUE;
 
     /* 'reset' dissection session */
-    epan_dissect_free(cf->edt);
-    cf->edt = NULL;
+    if (cf->edt) {
+      epan_dissect_free(cf->edt);
+      cf->edt = NULL;
+    }
     epan_free(cf->epan);
     cf->epan = ws_epan_new(cf);
     cf->cinfo.epan = cf->epan;