fixed NaN in JSON (fixes #225)

src/lib/ebus/datatype.cpp

@@ -696,6 +696,14 @@ result_t NumberDataType::readSymbols(size_t offset, size_t length, const SymbolS
         }
       }
 #endif
+      if (isnan(val)) {
+        if (outputFormat & OF_JSON) {
+          *output << "null";
+        } else {
+          *output << nullptr_VALUE;
+        }
+        return RESULT_OK;
+      }
       if (val != 0.0) {
         if (m_divisor < 0) {
           val *= static_cast<float>(-m_divisor);

src/lib/ebus/test/test_data.cpp

@@ -412,6 +412,7 @@ int main() {
     {"x,,exp", "-32.767", "10feffff04681103c2", "00", ""},
     {"x,,exp,1000", "-0.000090000",  "10feffff04ec51b8bd", "00", ""},
     {"x,,exp,-100", "-9",  "10feffff04ec51b8bd", "00", ""},
+    {"x,,exp", "-",      "10feffff040000c07f", "00", "W"},
     {"x,,exr", "-0.09",  "10feffff04bdb851ec", "00", ""},
     {"x,,exr", "0.0",    "10feffff0400000000", "00", ""},
     {"x,,exr", "-0.001", "10feffff04ba83126f", "00", ""},