-[cleanup]: added guard check to remove file only if it exists

AltStore/Operations/InstallAppOperation.swift

@@ -240,9 +240,11 @@ final class InstallAppOperation: ResultOperation<InstalledApp>
             
             do
             {
+                if(FileManager.default.fileExists(atPath: fileURL.path)){
                     try FileManager.default.removeItem(at: fileURL)
                     print("Removed refreshed IPA")
                 }
+            }
             catch
             {
                 print("Failed to remove refreshed .ipa: \(error)")