Error when getting an unset context without a default (#101)

Co-authored-by: centau <83140718+centau@users.noreply.github.com>

test/tests.luau

@@ -2828,6 +2828,16 @@ TEST("context()", function()
             end)
         end)
     end
+
+    do CASE "get context without default"
+        local ctx = context()
+
+        CHECK(not pcall(ctx))
+
+        root(function()
+            CHECK(not pcall(ctx))
+        end)
+    end
 end)
 
 TEST("nested effects cases", function()