macosx: fix crash in str_format_meta

(cherry picked from commit e823a595a8aa041de17e23d8f84bcb90d5d48702)
Signed-off-by: David Fuhrmann <dfuhrmann@videolan.org>

modules/gui/macosx/CoreInteraction.m

@@ -258,12 +258,14 @@ static VLCCoreInteraction *_o_sharedInstance = nil;
         return nil;
     }
 
-    NSString *o_name;
+    NSString *o_name = @"";
     char *format = var_InheritString(VLCIntf, "input-title-format");
+    if (format) {
         char *formated = str_format_meta(p_input, format);
         free(format);
-    o_name = [NSString stringWithUTF8String:formated];
+        o_name = toNSStr(formated);
         free(formated);
+    }
 
     NSURL * o_url = [NSURL URLWithString:[NSString stringWithUTF8String:psz_uri]];
     free(psz_uri);

modules/gui/macosx/MainWindow.m

@@ -695,14 +695,16 @@ static VLCMainWindow *_o_sharedInstance = nil;
     input_thread_t * p_input;
     p_input = pl_CurrentInput(VLCIntf);
     if (p_input) {
-        NSString *aString;
+        NSString *aString = @"";
 
         if (!config_GetPsz(VLCIntf, "video-title")) {
             char *format = var_InheritString(VLCIntf, "input-title-format");
+            if (format) {
                 char *formated = str_format_meta(p_input, format);
                 free(format);
-            aString = [NSString stringWithUTF8String:formated];
+                aString = toNSStr(formated);
                 free(formated);
+            }
         } else
             aString = [NSString stringWithUTF8String:config_GetPsz(VLCIntf, "video-title")];