Fix :setEffect("effect", true) and :getEffect("effect") when no filter is associated to the effect.

Fixes #1449

--HG--
branch : PabloMayobre/fix-seteffecteffect-true-and-geteffectef-1540253791471

src/modules/audio/wrap_Source.cpp

@@ -464,8 +464,10 @@ int w_Source_setEffect(lua_State *L)
 	Source *t = luax_checksource(L, 1);
 	const char *namestr = luaL_checkstring(L, 2);
 
+	const bool isBool = lua_gettop(L) == 3 && lua_isboolean(L, 3);
+
 	// :setEffect(effect, false) = clear effect
-	if (lua_gettop(L) == 3 && lua_isboolean(L, 3) && !lua_toboolean(L, 3))
+	if (isBool && !lua_toboolean(L, 3))
 	{
 		luax_catchexcept(L, [&]() { lua_pushboolean(L, t->unsetEffect(namestr)); });
 		return 1;
@@ -473,10 +475,11 @@ int w_Source_setEffect(lua_State *L)
 
 	std::map<Filter::Parameter, float> params;
 
-	if (setFilterReadFilter(L, 3, params) == 1)
-		luax_catchexcept(L, [&]() { lua_pushboolean(L, t->setEffect(namestr, params)); });
-	else
+	// :setEffect(effect, [true]) = set effect without filter
+	if (isBool || setFilterReadFilter(L, 3, params) == 0)
 		luax_catchexcept(L, [&]() { lua_pushboolean(L, t->setEffect(namestr)); });
+	else
+		luax_catchexcept(L, [&]() { lua_pushboolean(L, t->setEffect(namestr, params)); });
 	return 1;
 }
 
@@ -487,13 +490,20 @@ int w_Source_getEffect(lua_State *L)
 
 	std::map<Filter::Parameter, float> params;
 	if (!t->getEffect(namestr, params))
-		return 0;
+	{
+		luax_pushboolean(L, false);
+		return 1;
+	}
 
+	luax_pushboolean(L, true);
+
+	// No filter associated, return nil as second argument
 	if (params.size() == 0)
-		return 0;
+		return 1;
 
+	// Return filter settings as second argument
 	getFilterWriteFilter(L, 3, params);
-	return 1;
+	return 2;
 }
 
 int w_Source_getActiveEffects(lua_State *L)