Fix limited user cannot view himself's profile (#21212)

backport #21210, fix #21206

If user and viewer are equal the method should return true.
Also the common organization check was wrong as count can never be less then 0.

Tests are on main branch.

models/user/user.go

@@ -1265,7 +1265,7 @@ func isUserVisibleToViewerCond(viewer *User) builder.Cond {
 
 // IsUserVisibleToViewer check if viewer is able to see user profile
 func IsUserVisibleToViewer(ctx context.Context, u, viewer *User) bool {
-	if viewer != nil && viewer.IsAdmin {
+	if viewer != nil && (viewer.IsAdmin || viewer.ID == u.ID) {
 		return true
 	}
 
@@ -1304,7 +1304,7 @@ func IsUserVisibleToViewer(ctx context.Context, u, viewer *User) bool {
 			return false
 		}
 
-		if count < 0 {
+		if count == 0 {
 			// No common organization
 			return false
 		}