Throws error when player has no skin set / his skin is not stored in the database

[xknat]

Caused by: java.lang.NullPointerException: Cannot invoke "String.toLowerCase()" because "skinName" is null
	at net.skinsrestorer.shared.storage.SkinStorage.getSkinData(SkinStorage.java:171) ~[SkinsRestorer.jar:?]
	at net.skinsrestorer.api.SkinsRestorerAPI.getSkinData(SkinsRestorerAPI.java:135) ~[SkinsRestorer.jar:?]
	at net.skinsrestorer.api.SkinsRestorerAPI.getSkinTextureUrl(SkinsRestorerAPI.java:199) ~[SkinsRestorer.jar:?]
	at com.extendedclip.papi.expansion.skinsrestorer.SRWrapper.getSkinTextureUrl(SRWrapper.java:21) ~[?:?]
	at com.extendedclip.papi.expansion.skinsrestorer.SkinsRestorerExpansion.getSkinTextureUrl(SkinsRestorerExpansion.java:86) ~[?:?]
	at com.extendedclip.papi.expansion.skinsrestorer.SkinsRestorerExpansion.onRequest(SkinsRestorerExpansion.java:75) ~[?:?]
	at me.clip.placeholderapi.replacer.CharsReplacer.apply(CharsReplacer.java:119) ~[PlaceholderAPI-2.11.3.jar:?]
	at me.clip.placeholderapi.PlaceholderAPI.setPlaceholders(PlaceholderAPI.java:71) ~[PlaceholderAPI-2.11.3.jar:?]
	at me.clip.placeholderapi.commands.impl.local.CommandParse.evaluateParseSingular(CommandParse.java:117) ~[PlaceholderAPI-2.11.3.jar:?]
	at me.clip.placeholderapi.commands.impl.local.CommandParse.evaluate(CommandParse.java:57) ~[PlaceholderAPI-2.11.3.jar:?]
	at me.clip.placeholderapi.commands.PlaceholderCommandRouter.onCommand(PlaceholderCommandRouter.java:114) ~[PlaceholderAPI-2.11.3.jar:?]
	at org.bukkit.command.PluginCommand.execute(PluginCommand.java:45) ~[purpur-api-1.19.4-R0.1-SNAPSHOT.jar:?]
	```