commit 79b237917bf539605d9db4f50fa0beed1be862c3 (refs/remotes/origin/v3.5)
Author: Amos Jeffries <squid3@treenet.co.nz>
Date:   2017-07-08 21:58:09 +1200

    Ignore HTCP packets with invalid URI

diff --git a/src/htcp.cc b/src/htcp.cc
index c0241aa..55d08ff 100644
--- a/src/htcp.cc
+++ b/src/htcp.cc
@@ -749,9 +749,12 @@ htcpUnpackSpecifier(char *buf, int sz)
 
     s->request = HttpRequest::CreateFromUrlAndMethod(s->uri, method == Http::METHOD_NONE ? HttpRequestMethod(Http::METHOD_GET) : method);
 
-    if (s->request)
-        HTTPMSGLOCK(s->request);
+    if (!s->request) {
+        debugs(31, 3, "failed to create request. Invalid URI?");
+        return NULL;
+    }
 
+    HTTPMSGLOCK(s->request);
     return s;
 }