Tolerate Double.NaN when reading .xls files, see Bugzilla 49761

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1033004 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/poi/hssf/record/RecordInputStream.java

@@ -273,7 +273,10 @@ public final class RecordInputStream implements LittleEndianInput {
 		long valueLongBits = readLong();
 		double result = Double.longBitsToDouble(valueLongBits);
 		if (Double.isNaN(result)) {
-			throw new RuntimeException("Did not expect to read NaN"); // (Because Excel typically doesn't write NaN
+            // YK: Excel doesn't write NaN but instead converts the cell type into CELL_TYPE_ERROR.
+            // HSSF prior to version 3.7 had a bug: it could write Double.NaN but could not read such a file back.
+            // This behavior was fixed in POI-3.7.
+            //throw new RuntimeException("Did not expect to read NaN"); // (Because Excel typically doesn't write NaN
 		}
 		return result;
 	}

src/testcases/org/apache/poi/hssf/usermodel/TestHSSFCell.java

@@ -321,5 +321,10 @@ public final class TestHSSFCell extends BaseTestCell {
 		}
 	}
 
-
+    /**
+     * HSSF prior to version 3.7 had a bug: it could write a NaN but could not read such a file back.
+     */
+    public void testReadNaN() {
+        HSSFWorkbook wb = HSSFTestDataSamples.openSampleWorkbook("49761.xls");
+    }
 }