fix #2600 (segmentation fault of cppcheck ( enum{const} ))

lib/tokenize.cpp

@@ -7845,7 +7845,7 @@ void Tokenizer::simplifyEnum()
             }
 
             // check for a variable definition: enum {} x;
-            if (end->next()->str() != ";")
+            if (end->next() && end->next()->str() != ";")
             {
                 Token *tempTok = end;
 

test/testsimplifytokens.cpp

@@ -285,6 +285,7 @@ private:
         TEST_CASE(enum17); // ticket #2381 (duplicate enums)
         TEST_CASE(enum18); // #2466 (array with same name as enum constant)
         TEST_CASE(enum19); // ticket #2536
+        TEST_CASE(enum20); // ticket #2600
 
         // remove "std::" on some standard functions
         TEST_CASE(removestd);
@@ -6183,6 +6184,12 @@ private:
         ASSERT_EQUALS(";", tok(code, false));
     }
 
+    void enum20() // ticket #2600 segmentation fault
+    {
+        const char code[] = "enum { const }\n";
+        ASSERT_EQUALS(";", tok(code, false));
+    }
+
     void removestd()
     {
         ASSERT_EQUALS("; strcpy ( a , b ) ;", tok("; std::strcpy(a,b);"));