GDScript: Use path cache when checking preloaded scripts

The path itself might not always be set in some cases, especially when
the script is just created and is already in the resource cache. Using
get_path() in this case gets the correct resource path.

This also adds a null check for safety in case the path is incorrect or
missing, to avoid a crash in the engine.

modules/gdscript/gdscript_analyzer.cpp

@@ -3305,7 +3305,13 @@ GDScriptParser::DataType GDScriptAnalyzer::type_from_variant(const Variant &p_va
 						current = current->_owner;
 					}
 
-					Ref<GDScriptParserRef> ref = get_parser_for(current->path);
+					Ref<GDScriptParserRef> ref = get_parser_for(current->get_path());
+					if (ref.is_null()) {
+						push_error("Could not find script in path.", p_source);
+						GDScriptParser::DataType error_type;
+						error_type.kind = GDScriptParser::DataType::VARIANT;
+						return error_type;
+					}
 					ref->raise_status(GDScriptParserRef::INTERFACE_SOLVED);
 
 					GDScriptParser::ClassNode *found = ref->get_parser()->head;