SSH remoting: better error message for projects (#19320)

Before this, if no project paths were opened you were in a wierd UI
state where
most things didn't work because the project was ssh, but no
files/folders were open.

Release Notes:

- Fixed error handling when no project paths could be opened

crates/workspace/src/workspace.rs

@@ -5568,6 +5568,12 @@ pub fn open_ssh_project(
             };
         }
 
+        if project_paths_to_open.is_empty() {
+            return Err(project_path_errors
+                .pop()
+                .unwrap_or_else(|| anyhow!("no paths given")));
+        }
+
         cx.update_window(window.into(), |_, cx| {
             cx.replace_root_view(|cx| {
                 let mut workspace =