[java-atk-wrapper: 1/2] Check against ref_selection returning null

[Samuel Thibault <sthibaul src gnome org>]

commit 63f6f754e4b10ae7986497973fcf67eeff6b34a1
Author: Samuel Thibault <samuel thibault ens-lyon org>
Date:   Mon Apr 1 23:43:38 2019 +0200

    Check against ref_selection returning null
    
    Fixes https://bugzilla.gnome.org/show_bug.cgi?id=793544

 jni/src/jawselection.c | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/jni/src/jawselection.c b/jni/src/jawselection.c
index 1573cd2..a56ced2 100644
--- a/jni/src/jawselection.c
+++ b/jni/src/jawselection.c
@@ -129,6 +129,10 @@ jaw_selection_ref_selection (AtkSelection *selection, gint i)
        jclass classAtkSelection = (*jniEnv)->FindClass(jniEnv, "org/GNOME/Accessibility/AtkSelection");
        jmethodID jmid = (*jniEnv)->GetMethodID(jniEnv, classAtkSelection, "ref_selection", 
"(I)Ljavax/accessibility/Accessible;");
        jobject jchild = (*jniEnv)->CallObjectMethod(jniEnv, atk_selection, jmid, (jint)i);
+
+       if (!jchild) {
+               return NULL;
+       }
        
        jclass classAccessible = (*jniEnv)->FindClass( jniEnv, "javax/accessibility/Accessible" );
        jmid = (*jniEnv)->GetMethodID( jniEnv, classAccessible, "getAccessibleContext", 
"()Ljavax/accessibility/AccessibleContext;" );