detect: fix continue detection with amatch and tx

When using AMATCH, continue detection would fail if the tx part
had already run. This lead to start detection rerunning, causing
multiple alerts for the same issue.

src/detect-engine-state.c

@@ -528,14 +528,11 @@ void DeStateDetectContinueDetection(ThreadVars *tv, DetectEngineCtx *de_ctx,
         inspect_tx_id = AppLayerParserGetTransactionInspectId(f->alparser, flags);
         total_txs = AppLayerParserGetTxCnt(f->proto, alproto, alstate);
         inspect_tx = AppLayerParserGetTx(f->proto, alproto, alstate, inspect_tx_id);
-        if (inspect_tx == NULL) {
-            FLOWLOCK_UNLOCK(f);
-            SCMutexUnlock(&f->de_state_m);
-            return;
-        }
-        if (AppLayerParserGetStateProgress(f->proto, alproto, inspect_tx, flags) >=
-            AppLayerParserGetStateProgressCompletionStatus(f->proto, alproto, flags)) {
-            reset_de_state = 1;
+        if (inspect_tx != NULL) {
+            if (AppLayerParserGetStateProgress(f->proto, alproto, inspect_tx, flags) >=
+                    AppLayerParserGetStateProgressCompletionStatus(f->proto, alproto, flags)) {
+                reset_de_state = 1;
+            }
         }
         FLOWLOCK_UNLOCK(f);
         alproto_supports_txs = 1;