Fix script is loaded condition in effect commands (SkriptLang#4480)

Author: AyhamAl-Ali

src/main/java/ch/njol/skript/conditions/CondScriptLoaded.java

@@ -20,6 +20,7 @@
 
 import java.io.File;
 
+import ch.njol.skript.config.Config;
 import org.bukkit.event.Event;
 import org.eclipse.jdt.annotation.Nullable;
 
@@ -32,7 +33,7 @@
 import ch.njol.skript.doc.Since;
 import ch.njol.skript.lang.Condition;
 import ch.njol.skript.lang.Expression;
-import ch.njol.skript.lang.SkriptParser;
+import ch.njol.skript.lang.SkriptParser.ParseResult;
 import ch.njol.util.Kleenean;
 
 @Name("Is Script Loaded")
@@ -52,21 +53,27 @@ public class CondScriptLoaded extends Condition {
 	@Nullable
 	private File currentScriptFile;
 
-	@SuppressWarnings({"unchecked"})
 	@Override
-	public boolean init(Expression<?>[] exprs, int matchedPattern, Kleenean isDelayed, SkriptParser.ParseResult parseResult) {
+	@SuppressWarnings({"unchecked"})
+	public boolean init(Expression<?>[] exprs, int matchedPattern, Kleenean isDelayed, ParseResult parseResult) {
 		scripts = (Expression<String>) exprs[0];
 		setNegated(matchedPattern == 1);
-		assert getParser().getCurrentScript() != null;
-		currentScriptFile = getParser().getCurrentScript().getFile();
+		Config cs = getParser().getCurrentScript();
+		if (cs == null && scripts == null) {
+			Skript.error("The condition 'script loaded' requires a script name argument when used outside of script files");
+			return false;
+		} else if (cs != null) {
+			currentScriptFile = cs.getFile();
+		}
 		return true;
 	}
-	
+
 	@Override
 	public boolean check(Event e) {
-		Expression<String> scripts = this.scripts;
 		if (scripts == null) {
-			return ScriptLoader.getLoadedFiles().contains(currentScriptFile);
+			if (currentScriptFile == null)
+				return isNegated();
+			return ScriptLoader.getLoadedFiles().contains(currentScriptFile) ^ isNegated();
 		}
 
 		return scripts.check(e,
@@ -76,9 +83,8 @@ public boolean check(Event e) {
 
 	@Override
 	public String toString(@Nullable Event e, boolean debug) {
-		Expression<String> scripts = this.scripts;
-		
 		String scriptName;
+
 		if (scripts == null)
 			scriptName = "script";
 		else