functions -q: Return false without an argument

This erroneously listed functions and returned true.

src/builtin_functions.cpp

@@ -337,6 +337,11 @@ int builtin_functions(parser_t &parser, io_streams_t &streams, wchar_t **argv) {
         return STATUS_CMD_OK;
     }
 
+    // If we query with no argument, just return false.
+    if (opts.query && argc == optind) {
+        return STATUS_CMD_ERROR;
+    }
+
     if (opts.list || argc == optind) {
         wcstring_list_t names = function_get_names(opts.show_hidden);
         std::sort(names.begin(), names.end());

tests/function.err

@@ -29,3 +29,6 @@ fish: function: The name 'test' is reserved,
 and can not be used as a function name
 function test; echo banana; end
 ^
+
+####################
+# Checking `functions -q` without arguments

tests/function.in

@@ -48,4 +48,7 @@ diff (functions name3 | psub) (functions name3a | psub)
 
 logmsg Checking reserved names
 function test; echo banana; end
+
+logmsg Checking `functions -q` without arguments
+functions -q; or echo "False"
 exit 0

tests/function.out

@@ -73,3 +73,7 @@ Function name4 not found as expected
 
 ####################
 # Checking reserved names
+
+####################
+# Checking `functions -q` without arguments
+False