RNFetchBlob.fs.exists NullPointerException on Android with invalid path syntax

[tmaly1980]

Currently running 0.11.12 (latest) on RN 0.60.5. I've noticed that RNFetchBlob.fs.exists crashes with a NullPointerException on Android when the path provided has an invalid syntax. For example:

      path = "data:image/png;base64,asdasdasdasdasdasdasdasdasdasd" // Invalid path
      const pathExists = await RNFetchBlob.fs.exists(path);

I don't think this would be a common occurrence, but shouldn't the function gracefully fail when the file doesn't/cannot exist (ie due to an invalid path format), rather than let the app crash entirely? iOS is able to return gracefully without crashing.

[tmaly1980]

#470