Do not throw exception when incrementing search count of unknown term

Author: ahornace

suggester/src/main/java/org/opengrok/suggest/FieldWFSTCollection.java

@@ -370,7 +370,7 @@ public void incrementSearchCount(final Term term, final int value) {
         lock.readLock().lock();
         try {
             if (lookups.get(term.field()).get(term.text()) == null) {
-                throw new IllegalArgumentException("Unknown term " + term);
+                return; // unknown term
             }
 
             PopularityMap map = searchCountMaps.get(term.field());

suggester/src/test/java/org/opengrok/suggest/FieldWFSTCollectionTest.java

@@ -200,15 +200,6 @@ public void incrementByNegativeValueTest() throws IOException {
         f.incrementSearchCount(new Term("test", "example"), -10);
     }
 
-    @Test(expected = IllegalArgumentException.class)
-    public void incrementUnknownTermTest() throws IOException {
-        addText("test", "test case document");
-
-        init(true);
-
-        f.incrementSearchCount(new Term("test", "unknown"));
-    }
-
     @Test
     public void rebuildRemoveOldTermsTest() throws IOException {
         addText("test", "term");