detect/flowint: harden code

Make sure packet has a flow.

Related to bug #2288.

src/detect-flowint.c

@@ -95,6 +95,9 @@ int DetectFlowintMatch(ThreadVars *t, DetectEngineThreadCtx *det_ctx,
     uint32_t targetval;
     int ret = 0;
 
+    if (p->flow == NULL)
+        return 0;
+
     /** ATM If we are going to compare the current var with another
      * that doesn't exist, the default value will be zero;
      * if you don't want this behaviour, you can use the keyword

src/flow-var.c

@@ -53,6 +53,9 @@ static void FlowVarUpdateInt(FlowVar *fv, uint32_t value)
  */
 FlowVar *FlowVarGet(Flow *f, uint16_t idx)
 {
+    if (f == NULL)
+        return NULL;
+
     GenericVar *gv = f->flowvar;
 
     for ( ; gv != NULL; gv = gv->next) {