fix #2657 (segmentation fault of cppcheck ( gcc-testsuite: return f(){} ))

lib/symboldatabase.cpp

@@ -1455,7 +1455,7 @@ void Scope::getVariableList()
         // skip return and delete
         else if (Token::Match(tok, "return|delete"))
         {
-            while (tok->next()->str() != ";")
+            while (tok->next() && tok->next()->str() != ";")
                 tok = tok->next();
             continue;
         }

test/testclass.cpp

@@ -197,6 +197,7 @@ private:
         TEST_CASE(symboldatabase14); // ticket #2589
         TEST_CASE(symboldatabase15); // ticket #2591
         TEST_CASE(symboldatabase16); // ticket #2637
+        TEST_CASE(symboldatabase17); // ticket #2657
     }
 
     // Check the operator Equal
@@ -5805,6 +5806,14 @@ private:
         ASSERT_EQUALS("", errout.str());
     }
 
+    void symboldatabase17()
+    {
+        // ticket #2657 - segmentation fault
+        checkConst("return f(){}\n");
+
+        ASSERT_EQUALS("", errout.str());
+    }
+
 };
 
 REGISTER_TEST(TestClass)