Fix rare startup bug in case there is a time but no date (ros-drivers…

…#144)

Signed-off-by: Gabriel Gaessler <[email protected]>

src/libnmea_navsat_driver/parser.py

@@ -156,7 +156,7 @@ def convert_time_rmc(date_str, time_str):
         tuple(float, float): 2-tuple of (NaN, NaN) if the sentence does not contain valid time.
     """
     # If one of the time fields is empty, return NaN seconds
-    if not time_str[0:2] or not time_str[2:4] or not time_str[4:6]:
+    if not date_str[0:6] or not time_str[0:2] or not time_str[2:4] or not time_str[4:6]:
         return (float('NaN'), float('NaN'))
 
     pc_year = datetime.date.today().year