fix: check that numeric value exists (#12042)

Check that a value exists for buildIdentifier
before parsing integer.

Fixes #12041

flow-server/src/main/java/com/vaadin/flow/server/frontend/FrontendVersion.java

@@ -338,6 +338,12 @@ private int compareBuildIdentifier(FrontendVersion other) {
                 return thisMatcher.group(1)
                         .compareToIgnoreCase(otherMatcher.group(1));
             }
+            // if one or both are missing numeric value do not parse int
+            if (thisMatcher.group(2).isEmpty()
+                    || otherMatcher.group(2).isEmpty()) {
+                return buildIdentifier
+                        .compareToIgnoreCase(other.buildIdentifier);
+            }
             return Integer.parseInt(thisMatcher.group(2))
                     - Integer.parseInt(otherMatcher.group(2));
         }

flow-server/src/test/java/com/vaadin/flow/server/frontend/FrontendVersionTest.java

@@ -3,6 +3,7 @@
 import org.junit.Assert;
 import org.junit.Test;
 
+import static com.helger.commons.mock.CommonsAssert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
@@ -77,6 +78,18 @@ public void testIsEqualTo() {
                 fromString.isEqualTo(fromConstructor));
     }
 
+    @Test // #12041
+    public void testSimilarBuildIdentifiers() {
+        FrontendVersion version = new FrontendVersion("1.1.1-SNAPSHOT");
+        FrontendVersion equals = new FrontendVersion("1.1.1-SNAPSHOT");
+
+        assertTrue("Versions be the same", version.isEqualTo(equals));
+        assertFalse("Version should not be older", version.isOlderThan(equals));
+        assertEquals("Versions should not have a difference", 0,
+                version.compareTo(equals));
+        assertFalse("Version should not be newer", version.isNewerThan(equals));
+    }
+
     @Test(expected = NumberFormatException.class)
     public void faultyStringVersion_throwsException() {
         new FrontendVersion("12.0b.1");