Only call fs.realpathSync() if the file exists

Files which are deleted that Atom currently has open will have a path but won’t actually exist in the file system. This caused us to throw a TypeError (see #168). To avoid this, we simply use the path returned by TextEditor::getPath() if the file does not exist.

To avoid confusion, I have also renamed the `relativeActivePanePath` and `activePanePath` variables to a single `activePanePath` variable.

Fixes #168 and closes #174.

lib/utils/style-settings.js

@@ -26,17 +26,22 @@ function checkStyleSettings (filePath) {
       return settings
     }
 
-    var relativeActivePanePath = activePane.getPath()
+    var activePanePath = activePane.getPath()
 
-    if (!relativeActivePanePath) {
+    if (!activePanePath) {
       settings.style = 'no-style'
       return settings
     }
 
-    var absoluteActivePanePath = fs.realpathSync(relativeActivePanePath)
+    try {
+      activePanePath = fs.realpathSync(activePanePath)
+    } catch (e) {
+      if (e.code !== 'ENOENT') throw e
+    }
+
     var projectPaths = atom.project.getPaths()
 
-    projectPath = projectPaths.find((p) => absoluteActivePanePath.indexOf(fs.realpathSync(p)) >= 0)
+    projectPath = projectPaths.find((p) => activePanePath.indexOf(fs.realpathSync(p)) >= 0)
   } catch (e) {
     console.error('Could not get project path', e)
     return