Fix exception in AntPathMatcher for leading *

Issue: SPR-13139

Author: martinlippert

spring-core/src/main/java/org/springframework/util/AntPathMatcher.java

@@ -740,7 +740,7 @@ else if (this.pattern.charAt(pos) == '*') {
 							this.doubleWildcards++;
 							pos += 2;
 						}
-						else if (!this.pattern.substring(pos - 1).equals(".*")) {
+						else if (pos > 0 && !this.pattern.substring(pos - 1).equals(".*")) {
 							this.singleWildcards++;
 							pos++;
 						}

spring-core/src/test/java/org/springframework/util/AntPathMatcherTests.java

@@ -474,6 +474,10 @@ public void patternComparator() {
 
 		// longer is better
 		assertEquals(1, comparator.compare("/hotels", "/hotels2"));
+		
+		//SPR-13139
+		assertEquals(-1, comparator.compare("*", "*/**"));
+		assertEquals(1, comparator.compare("*/**", "*"));
 	}
 
 	@Test