fix: Fix double backslash before escaped unicode character causing lexing error

Author: win32kbase

src/main/java/me/coley/recaf/util/EscapeUtil.java

@@ -151,10 +151,17 @@ private static int computeEscapeUnicode(String input, int cursor, StringBuilder
 		if (cursor + 1 >= input.length()) {
 			return 0;
 		}
+
+		// Check for double backslash in prefix "\\\\u" in "\\\\uXXXX"
+		boolean initialEscape = input.charAt(cursor) == '\\' && input.charAt(cursor + 1) == '\\';
+
 		// Check prefix "\\u" in "\\uXXXX"
-		if (input.charAt(cursor) != '\\' || input.charAt(cursor + 1) != 'u') {
-			return 0;
+		if (!initialEscape) {
+			if (input.charAt(cursor) != '\\' || input.charAt(cursor + 1) != 'u') {
+				return 0;
+			}
 		}
+
 		// Compute escape size, initial is 2 for the "\\u"
 		int len = 2;
 		// Combined:
@@ -171,10 +178,17 @@ private static int computeEscapeUnicode(String input, int cursor, StringBuilder
 		}
 		// Bounds check, then fetch hex value and store in builder, then return total consumed length
 		if (cursor + len + 4 <= input.length()) {
+			String substring = input.substring(cursor, cursor + len + 4);
+
+			if (initialEscape) {
+				builder.append(substring);
+				return len + 4;
+			}
+
 			String unicode = input.substring(cursor + len, cursor + len + 4);
 			try {
 				int value = Integer.parseInt(unicode, 16);
-				builder.append(value != TERMINATOR ? (char) value : input.substring(cursor, cursor + len + 4));
+				builder.append(value != TERMINATOR ? (char) value : substring);
 			} catch(NumberFormatException ignored) {
 				return 0;
 			}