Test crashes when using empty GET parameter #44

diff --git a/src/webserver.cpp b/src/webserver.cpp
index 9858bff..a0ea97f 100644
--- a/src/webserver.cpp
+++ b/src/webserver.cpp
@@ -749,9 +749,16 @@ int webserver::build_request_args (
         void *cls,
         enum MHD_ValueKind kind,
         const char *key,
-        const char *value
+        const char *orig_value
 )
 {
+    int size;
+    char *value;
+    if (orig_value == NULL)
+        value = (char*) "";
+    else
+        value = (char*) orig_value;
+
     details::modded_request* mr = static_cast<details::modded_request*>(cls);
     {
         char buf[strlen(key) + strlen(value) + 3];
@@ -766,7 +773,11 @@ int webserver::build_request_args (
             mr->dhr->querystring += string(buf);
         }
     }
-    int size = internal_unescaper((void*) mr->ws, (char*) value);
+
+    if (orig_value == NULL)
+        size = 0;
+    else
+        size = internal_unescaper((void*) mr->ws, value);
     mr->dhr->set_arg(key, string(value, size));
     return MHD_YES;
 }