C++: Add false positive testcase involving assignments.

Author: MathiasVP

cpp/ql/test/experimental/query-tests/Security/CWE/CWE-570/semmle/tests/IncorrectAllocationErrorHandling.expected

@@ -16,3 +16,4 @@
 | test.cpp:151:9:151:24 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:152:15:152:18 | { ... } | This catch block |
 | test.cpp:199:15:199:35 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:201:16:201:19 | { ... } | This catch block |
 | test.cpp:212:14:212:34 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:213:34:213:36 | { ... } | This catch block |
+| test.cpp:219:9:219:15 | new | This allocation cannot throw. $@ is unnecessary. | test.cpp:220:34:220:36 | { ... } | This catch block |

cpp/ql/test/experimental/query-tests/Security/CWE/CWE-570/semmle/tests/test.cpp

@@ -212,3 +212,10 @@ void bad_new_catch_baseclass_of_bad_alloc() {
     int* p = new(std::nothrow) int; // BAD
   } catch(const std::exception&) { }
 }
+
+void good_new_catch_exception_in_assignment() {
+  int* p;
+  try {
+    p = new int; // GOOD [FALSE POSITIVE]
+  } catch(const std::bad_alloc&) { }
+}