Fix number formatting when cells are empty

lib/roo/excelx/cell/number.rb

@@ -18,6 +18,8 @@ def initialize(value, formula, excelx_type, style, link, coordinate)
 
         def create_numeric(number)
           return number if Excelx::ERROR_VALUES.include?(number)
+          return nil if (number.nil? || number == "")
+
           case @format
           when /%/
             Float(number)
@@ -30,6 +32,7 @@ def create_numeric(number)
 
         def formatted_value
           return @cell_value if Excelx::ERROR_VALUES.include?(@cell_value)
+          return '' if  (@cell_value.nil? || @cell_value == "")
 
           formatter = generate_formatter(@format)
           if formatter.is_a? Proc

spec/lib/roo/excelx/cell/number_spec.rb

@@ -0,0 +1,55 @@
+require 'spec_helper'
+
+RSpec.describe Roo::Excelx::Cell::Number do
+
+  describe '#initialize' do
+    let(:formula)     { nil }
+    let(:excelx_type) { [:numeric_or_formula, format] }
+    let(:format)      { "#,##0.00" }
+    let(:style)       { 1 }
+    let(:link)        { nil }
+    let(:coordinate)  { [1,1] }
+
+    let(:number)  { Roo::Excelx::Cell::Number.new(value, formula, excelx_type, style, link, coordinate)}
+
+    context 'with an actual value' do
+      let(:value)       { 0.1 }
+      it 'creates the object and parses the value' do
+        expect(number.value).to eq 0.1
+      end
+    end
+
+    context 'with an empty value' do
+      let(:value)       { "" }
+      it 'creates the object with a nil value' do
+        expect(number.value).to eq nil
+      end
+    end
+  end
+
+  describe '#formatted_value' do
+    let(:formula)     { nil }
+    let(:excelx_type) { [:numeric_or_formula, format] }
+    let(:format)      { "#,##0.00" }
+    let(:style)       { 1 }
+    let(:link)        { nil }
+    let(:coordinate)  { [1,1] }
+
+    let(:number)  { Roo::Excelx::Cell::Number.new(value, formula, excelx_type, style, link, coordinate)}
+
+    context 'with an actual value' do
+      let(:value)       { 0.1 }
+      it 'creates the object and parses the value' do
+        expect(number.formatted_value).to eq '0.10'
+      end
+    end
+
+    context 'with an empty value' do
+      let(:value)       { "" }
+      it 'creates the object with a nil value' do
+        expect(number.formatted_value).to eq ''
+      end
+    end
+
+  end
+end