winedbg: Avoid a compiler warning about "use of uninitialized" in in types_extract_as_longlong.

programs/winedbg/types.c

@@ -123,7 +123,7 @@ LONGLONG types_extract_as_longlong(const struct dbg_lvalue* lvalue,
     default:
         WINE_FIXME("Unsupported tag %u\n", tag);
         RaiseException(DEBUG_STATUS_NOT_AN_INTEGER, 0, 0, NULL);
-        break;
+        rtn = 0;
     }
 
     return rtn;