libluna: Treat a negative precision as if precision was omitted

libluna/src/Format.cpp

@@ -139,7 +139,10 @@ static usize parse_precision(const char** format, flags_t& flags, va_list ap)
             const int precision = va_arg(ap, int);
             if (precision >= 0) result = (usize)precision;
             else
+            {
                 result = 0;
+                flags &= ~FLAG_USE_PRECISION;
+            }
             (*format)++;
         }
     }