Fix behavior on empty completion request

application/argumentparser.cpp

@@ -665,9 +665,11 @@ void ArgumentParser::readArgs(int argc, const char * const *argv)
                 // the first argument after "--bash-completion-for" is the index of the current word
                 try {
                     currentWordIndex = (--argc ? stringToNumber<unsigned int, string>(*(++argv)) : 0);
-                    ++argv, --argc;
                 } catch(const ConversionException &) {
-                    currentWordIndex = static_cast<unsigned int>(argc - 1);
+                    currentWordIndex = static_cast<unsigned int>(argc);
+                }
+                if(argc) {
+                    ++argv, --argc;
                 }
             }