fix: Fix too-long-variable-name throwing exception on Set X Variable without arguments (#1675)

Author: bhirsz

src/robocop/linter/rules/lengths.py

@@ -985,10 +985,13 @@ def visit_KeywordCall(self, node: KeywordCall) -> None:  # noqa: N802
             return
         for variable in node.get_tokens(Token.ASSIGN):
             self.add_variable_to_scope(variable, strip_equals_from_assignment(variable.value))
-        if normalize_robot_name(node.keyword) in self.set_variable_keywords:  # Only check args of 'Set ... Variable'
-            argument = node.get_token(Token.ARGUMENT)
-            if argument.value.startswith(tuple(self.var_identifiers + "\\")):  # Otherwise this is invalid RF syntax
-                self.add_variable_to_scope(argument)
+        # Only check args of 'Set ... Variable' and check for invalid RF syntax
+        if (
+            normalize_robot_name(node.keyword) in self.set_variable_keywords
+            and (argument := node.get_token(Token.ARGUMENT))
+            and argument.value.startswith(tuple(self.var_identifiers + "\\"))
+        ):
+            self.add_variable_to_scope(argument)
 
     def visit_Var(self, node: Statement) -> None:  # noqa: N802
         if variable := node.get_token(Token.VARIABLE):

tests/linter/rules/lengths/too_long_variable_name/test.robot

@@ -113,3 +113,5 @@ Keyword With ${short_embedded_argument_name} And ${embedded_argument_name_that_i
 Keyword ${embedded_just_shy_of_max_len_contains:pattern} And ${embedded_name_that_is_too_long_that_contains:pattern}    # 44
     Log    ${embedded_just_shy_of_max_len_contains}
 
+Test Invalid Syntax
+    Set Suite Variable  # no argument