If dringXcontext is null, fallback to default context value.

(closes issue #17693)
Reported by: iasgoscouk
Patches:
      issue17693.patch uploaded by pabelanger (license 224)
Tested by: iasgoscouk

Review: https://reviewboard.asterisk.org/r/803/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@279755 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_dahdi.c

@@ -1825,8 +1825,8 @@ static int my_distinctive_ring(struct ast_channel *chan, void *pvt, int idx, int
 
 			if (distMatches == 3) {
 				/* The ring matches, set the context to whatever is for distinctive ring.. */
-				ast_copy_string(p->context, p->drings.ringContext[counter].contextData, sizeof(p->context));
-				ast_copy_string(chan->context, p->drings.ringContext[counter].contextData, sizeof(chan->context));
+				ast_copy_string(p->context, S_OR(p->drings.ringContext[counter].contextData, p->defcontext), sizeof(p->context));
+				ast_copy_string(chan->context, S_OR(p->drings.ringContext[counter].contextData, p->defcontext), sizeof(chan->context));
 				ast_verb(3, "Distinctive Ring matched context %s\n",p->context);
 				break;
 			}
@@ -10184,8 +10184,8 @@ static void *analog_ss_thread(void *data)
 
 							if (distMatches == 3) {
 								/* The ring matches, set the context to whatever is for distinctive ring.. */
-								ast_copy_string(p->context, p->drings.ringContext[counter].contextData, sizeof(p->context));
-								ast_copy_string(chan->context, p->drings.ringContext[counter].contextData, sizeof(chan->context));
+								ast_copy_string(p->context, S_OR(p->drings.ringContext[counter].contextData, p->defcontext), sizeof(p->context));
+								ast_copy_string(chan->context, S_OR(p->drings.ringContext[counter].contextData, p->defcontext), sizeof(chan->context));
 								ast_verb(3, "Distinctive Ring matched context %s\n",p->context);
 								break;
 							}
@@ -10422,8 +10422,8 @@ static void *analog_ss_thread(void *data)
 							}
 							if (distMatches == 3) {
 								/* The ring matches, set the context to whatever is for distinctive ring.. */
-								ast_copy_string(p->context, p->drings.ringContext[counter].contextData, sizeof(p->context));
-								ast_copy_string(chan->context, p->drings.ringContext[counter].contextData, sizeof(chan->context));
+								ast_copy_string(p->context, S_OR(p->drings.ringContext[counter].contextData, p->defcontext), sizeof(p->context));
+								ast_copy_string(chan->context, S_OR(p->drings.ringContext[counter].contextData, p->defcontext), sizeof(chan->context));
 								ast_verb(3, "Distinctive Ring matched context %s\n",p->context);
 								break;
 							}