Fix possible issue wrt FasterXML#181 (although not reproducible on 2.4)

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/core/json/ReaderBasedJsonParser.java

@@ -1047,7 +1047,7 @@ private final JsonToken _parseNumber2(boolean neg, int startPtr) throws IOExcept
         }
         // Also, integer part is not optional
         if (intLen == 0) {
-            reportInvalidNumber("Missing integer part (next char "+_getCharDesc(c)+")");
+            return _handleInvalidNumberStart(c, neg);
         }
 
         int fractLen = 0;