rename tutorial 'Checking slots' -> 'Checking for slot content'

site/content/tutorial/14-composition/04-optional-slots/text.md

@@ -1,5 +1,5 @@
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-title: Checking slots
+title: Checking for slot content
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 In some cases, you may want to control parts of your component based on whether the parent passes in content for a certain slot. Perhaps you have a wrapper around that slot, and you don't want to render it if the slot is empty. Or perhaps you'd like to apply a class only if the slot is present. You can do this by checking the properties of the special `$$slots` variable.