macosx/open: added missing sanity checks

(cherry picked from commit e139c96cdabca52827db8843d9aaa41eb50460a1)

modules/gui/macosx/open.m

@@ -701,10 +701,13 @@ static VLCOpen *_o_sharedMainInstance = nil;
                                 NULL,
                                 NULL
                                 );
-        if ( noErr == err ) {
+        if ( noErr == err )
             actualVolume = catalogInfo.volume;
+        else
+            return @"";
     }
-    }
+    else
+        return @"";
 
     GetVolParmsInfoBuffer volumeParms;
     err = FSGetVolumeParms( actualVolume, &volumeParms, sizeof(volumeParms) );
@@ -734,10 +737,13 @@ static VLCOpen *_o_sharedMainInstance = nil;
                                 NULL,
                                 NULL
                                 );
-        if ( noErr == err ) {
+        if ( noErr == err )
             actualVolume = catalogInfo.volume;
+        else
+            return NULL;
     }
-    }
+    else
+        return NULL;
 
     GetVolParmsInfoBuffer volumeParms;
     err = FSGetVolumeParms( actualVolume, &volumeParms, sizeof(volumeParms) );
@@ -745,6 +751,9 @@ static VLCOpen *_o_sharedMainInstance = nil;
     CFMutableDictionaryRef matchingDict;
     io_service_t service;
 
+    if (!volumeParms.vMDeviceID)
+        return NULL;
+
     matchingDict = IOBSDNameMatching(kIOMasterPortDefault, 0, volumeParms.vMDeviceID);
     service = IOServiceGetMatchingService(kIOMasterPortDefault, matchingDict);