Remove redundant length check in isBlank (#1516)

Author: yuanchaodu

src/main/java/org/apache/commons/lang3/StringUtils.java

@@ -3506,9 +3506,6 @@ public static boolean isAsciiPrintable(final CharSequence cs) {
      */
     public static boolean isBlank(final CharSequence cs) {
         final int strLen = length(cs);
-        if (strLen == 0) {
-            return true;
-        }
         for (int i = 0; i < strLen; i++) {
             if (!Character.isWhitespace(cs.charAt(i))) {
                 return false;