Only enable splitting algorithm under certain conditions

[manjitapandey]

Is your feature request related to a problem? Please describe.

Issue 1:

• Task splitting algorithm only supports polygons.
• So we encountered error when trying to split task using task splitting algorithm.

Issue 2:

• Task splitting algorithm must be provided polygons, divided by linestrings (e.g. roads, rivers, etc).

Describe the solution you'd like

• If the geojson is not predominantly polygons, or if there are no linestrings present, then show the user a warning that splitting may not work: 'the splitting algorithm is only valid for use with building data, including linear features such as roads/rivers'.