HTTP parser: fixed handling header fields with missing colon.

src/nxt_http_parse.c

@@ -482,7 +482,9 @@ name_end:
         return nxt_http_parse_field_value(rp, pos, end);
     }
 
-    *pos = &p[i];
+    if (nxt_slow_path(i != 0)) {
+        return NXT_ERROR;
+    }
 
     rp->field_name.length = 0;
 

test/nxt_http_parse_unit_test.c

@@ -219,6 +219,18 @@ static nxt_http_parse_unit_test_case_t  nxt_http_unit_test_cases[] = {
         NXT_DONE,
         NULL, { NULL }
     },
+    {
+        nxt_string("GET / HTTP/1.1\r\n"
+                   "Host:\r\n\r\n"),
+        NXT_DONE,
+        NULL, { NULL }
+    },
+    {
+        nxt_string("GET / HTTP/1.1\r\n"
+                   "Host example.com\r\n\r\n"),
+        NXT_ERROR,
+        NULL, { NULL }
+    },
     {
         nxt_string("GET / HTTP/1.1\r\n"
                    ":Host: example.com\r\n\r\n"),