Make load() work after a clean start

At the cost of making it drop the current table.
However, it shouldn't be a big deal ergonomics-wise, since `load()` is most often used
when the current table is empty in order to populate it.

Author: erszcz

src/tr.erl

@@ -306,7 +306,7 @@ set_tab(Tab) when is_atom(Tab) ->
 
 %% @doc Loads an ETS trace table from a file, and makes it the current table.
 %%
-%% Fails if the table already exists.
+%% Overwrites the current table if it exists.
 -spec load(file:name_all()) -> {ok, table()} | {error, any()}.
 load(File) when is_binary(File) ->
     load(binary_to_list(File));
@@ -566,6 +566,12 @@ handle_call({dump, File}, _From, State = #{tab := Tab}) ->
     Reply = ets:tab2file(Tab, File),
     {reply, Reply, State};
 handle_call({load, File}, _From, State) ->
+    case ets:info(maps:get(tab, State), id) of
+        undefined ->
+            ok;
+        _ ->
+            ets:delete(maps:get(tab, State))
+    end,
     Reply = ets:file2tab(File),
     NewState = case Reply of
                    {ok, Tab} -> State#{tab := Tab, index := index(Tab)};