fix #3015

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/parsers/smt2/smt2scanner.cpp

@@ -379,7 +379,7 @@ namespace smt2 {
 
     char const * scanner::cached_str(unsigned begin, unsigned end) {
         m_cache_result.reset();
-        while (isspace(m_cache[begin]) && begin < end)
+        while (begin < end && isspace(m_cache[begin]))
             begin++;
         while (begin < end && isspace(m_cache[end-1]))
             end--;

src/parsers/smt2/smt2scanner.h

@@ -102,6 +102,7 @@ namespace smt2 {
         void stop_caching() { m_cache_input = false; }
         unsigned cache_size() const { return m_cache.size(); }
         void reset_cache() { m_cache.reset(); }
+
         char const * cached_str(unsigned begin, unsigned end);
     };