Fix potential parsing issue in threshold code.

src/detect-threshold.c

@@ -121,6 +121,8 @@ static DetectThresholdData *DetectThresholdParse (char *rawstr)
     int i = 0;
 
     copy_str = SCStrdup(rawstr);
+    if (copy_str == NULL)
+        goto error;
 
     for(pos = 0, threshold_opt = strtok(copy_str,",");  pos < strlen(copy_str) &&  threshold_opt != NULL;  pos++, threshold_opt = strtok(NULL,",")) {
 
@@ -134,8 +136,7 @@ static DetectThresholdData *DetectThresholdParse (char *rawstr)
             track_found++;
     }
 
-    if(copy_str)
-        SCFree(copy_str);
+    SCFree(copy_str);
 
     if(count_found != 1 || second_found != 1 || type_found != 1 || track_found != 1)
         goto error;