fix: ConcurrentModificationException in TokenizerThread #841

Author: sebthom

org.eclipse.tm4e.core/src/main/java/org/eclipse/tm4e/core/internal/theme/Theme.java

@@ -16,10 +16,11 @@
 
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
 
 import org.eclipse.jdt.annotation.Nullable;
 import org.eclipse.tm4e.core.internal.grammar.ScopeStack;
@@ -54,7 +55,7 @@ public static Theme createFromParsedTheme(final List<ParsedThemeRule> source, @N
 		return resolveParsedThemeRules(source, colorMap);
 	}
 
-	private final Map<String /* scopeName */, List<ThemeTrieElementRule>> _cachedMatchRoot = new HashMap<>();
+	private final ConcurrentMap<String /* scopeName */, List<ThemeTrieElementRule>> _cachedMatchRoot = new ConcurrentHashMap<>();
 
 	private final ColorMap _colorMap;
 	private final StyleAttributes _defaults;