Handle None in validate_emsdk_version

Author: hoodmane

Platforms/emscripten/__main__.py

@@ -79,6 +79,8 @@ def get_build_paths(cross_build_dir=None, emsdk_cache=None):
 
 def validate_emsdk_version(emsdk_cache):
     """Validate that the emsdk cache contains the required emscripten version."""
+    if emsdk_cahce is None:
+        return
     required_version = required_emscripten_version()
     emsdk_env = emsdk_activate_path(emsdk_cache)
     if not emsdk_env.is_file():