Index: oak-core/src/main/java/org/apache/jackrabbit/oak/security/principal/PrincipalProviderImpl.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/security/principal/PrincipalProviderImpl.java	(revision 1856270)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/security/principal/PrincipalProviderImpl.java	(date 1553248439000)
@@ -136,7 +136,7 @@
 
     @NotNull
     @Override
-    public Iterator<? extends Principal> findPrincipals(final String nameHint, final boolean fullText, final int searchType, long offset,
+    public Iterator<? extends Principal> findPrincipals(@Nullable final String nameHint, final boolean fullText, final int searchType, long offset,
             long limit) {
         if (offset < 0) {
             offset = 0;
Index: oak-core/src/main/java/org/apache/jackrabbit/oak/security/user/UserPrincipalProvider.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- oak-core/src/main/java/org/apache/jackrabbit/oak/security/user/UserPrincipalProvider.java	(revision 1856270)
+++ oak-core/src/main/java/org/apache/jackrabbit/oak/security/user/UserPrincipalProvider.java	(date 1553248439000)
@@ -155,14 +155,15 @@
         return principals;
     }
 
+    @NotNull
     @Override
-    public Iterator<? extends Principal> findPrincipals(final String nameHint, final int searchType) {
+    public Iterator<? extends Principal> findPrincipals(@Nullable final String nameHint, final int searchType) {
         return findPrincipals(nameHint, false, searchType, 0, -1);
     }
 
     @NotNull
     @Override
-    public Iterator<? extends Principal> findPrincipals(final String nameHint, final boolean fullText, final int searchType, long offset,
+    public Iterator<? extends Principal> findPrincipals(@Nullable final String nameHint, final boolean fullText, final int searchType, long offset,
             long limit) {
         if (offset < 0) {
             offset = 0;