Allow try-catches to take non-lists in body

The routine detecting the catch and finally parts was assuming its
inputs are always lists, leading to errors when passed an atom or
string.

Fixes anko#30.

src/built-in-macros.ls

@@ -361,6 +361,7 @@ contents =
   \try : ({compile, compile-many}:env, ...args) ->
 
     is-part = (thing, clause-name) ->
+      if not (thing instanceof list) then return false
       first = thing.content.0
       (first instanceof atom) && (first.text! is clause-name)
 

test.ls

@@ -406,6 +406,23 @@ test "try-catch (with `catch` and `finally`)" ->
       }
       """
 
+test "try-catch (with plain atom in body)" ->
+  esl '''
+      (try foo
+           (catch e
+                  bar)
+           (finally baz))
+      '''
+    ..`@equals` """
+      try {
+          foo;
+      } catch (e) {
+          bar;
+      } finally {
+          baz;
+      }
+      """
+
 test "try-catch (with empty body, `catch` and `finally`)" ->
   esl '''
       (try (catch err)