fix: Exception on empty screen

[wizlif]

@Edamijueda and I decided to fix Issue #335 . Turns out the spotlight header doesn't act well without data. This was due to the ExpandablePageView and DotsIndicator throwing exceptions when offered an empty list. For now we've created skeleton loaders but will still need the empty designs as we go forward.

Closes #335

[codecov[bot]]

Codecov Report

Merging #337 (9468742) into development (1ac5990) will increase coverage by 2.55%. The diff coverage is 98.18%.

@@               Coverage Diff               @@
##           development     #337      +/-   ##
===============================================
+ Coverage        36.70%   39.25%   +2.55%     
===============================================
  Files              144      147       +3     
  Lines             3749     3834      +85     
===============================================
+ Hits              1376     1505     +129     
+ Misses            2373     2329      -44     

Impacted Files	Coverage Δ
.../crowdaction_home/widgets/in_spotlight_header.dart	3.70% <0.00%> (+1.37%)	:arrow_up:
...spotlight_crowdactions/spotlight_crowdactions.dart	95.45% <95.45%> (ø)
...tlight_crowdactions/in_spotlight_header_empty.dart	100.00% <100.00%> (ø)
...entation/home/widgets/current_upcoming_layout.dart	90.69% <100.00%> (+87.66%)	:arrow_up:
...shared_widgets/micro_crowdaction_card_loading.dart	100.00% <100.00%> (ø)
.../presentation/shared_widgets/crowdaction_card.dart	96.29% <0.00%> (+1.85%)	:arrow_up:

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