fix(presets): use empty table when no build presets are defined (#325)

Author: Denzel

lua/cmake-tools/presets.lua

@@ -125,7 +125,7 @@ function Presets:parse(cwd)
     preset = createPreset(preset)
   end
 
-  for _, build_preset in ipairs(instance.buildPresets) do
+  for _, build_preset in ipairs(instance.buildPresets or {}) do
     build_preset = createBuildPreset(build_preset)
   end