Use cursor indent level if commenting single line

Previously commenting a line of all whitespace would insert
the comment at column 0 on the line since blank lines are
ignored when calculating the minimum indent level.

spec/language-mode-spec.coffee

@@ -46,6 +46,16 @@ describe "LanguageMode", ->
         languageMode.toggleLineCommentsForBufferRows(0, 0)
         expect(buffer.lineForRow(0)).toBe " // var i;"
 
+        buffer.setText('  ')
+        languageMode.toggleLineCommentsForBufferRows(0, 0)
+        expect(buffer.lineForRow(0)).toBe "  // "
+
+        buffer.setText ('    a\n  \n    b')
+        languageMode.toggleLineCommentsForBufferRows(0, 2)
+        expect(buffer.lineForRow(0)).toBe "    // a"
+        expect(buffer.lineForRow(1)).toBe "    // "
+        expect(buffer.lineForRow(2)).toBe "    // b"
+
     describe ".rowRangeForCodeFoldAtBufferRow(bufferRow)", ->
       it "returns the start/end rows of the foldable region starting at the given row", ->
         expect(languageMode.rowRangeForCodeFoldAtBufferRow(0)).toEqual [0, 12]

src/language-mode.coffee

@@ -74,7 +74,10 @@ class LanguageMode
             columnEnd = columnStart + match[2].length
             buffer.change([[row, columnStart], [row, columnEnd]], "")
       else
-        indent = @minIndentLevelForRowRange(start, end)
+        if start is end
+          indent = @editor.indentationForBufferRow(start)
+        else
+          indent = @minIndentLevelForRowRange(start, end)
         indentString = @editor.buildIndentString(indent)
         tabLength = @editor.getTabLength()
         indentRegex = new RegExp("(\t|[ ]{#{tabLength}}){#{Math.floor(indent)}}")