Fix for BUG#12414917 - ISCLOSED() CRASHES ON 64-BIT BUILDS

Problem:      
lack of incoming geometry data validation may 
lead to a server crash when ISCLOSED() function called.

Solution:
necessary incoming data check added.

mysql-test/r/gis.result

@@ -1075,4 +1075,10 @@ SPATIAL INDEX i1 (col1, col2)
 );
 ERROR HY000: Incorrect arguments to SPATIAL INDEX
 DROP TABLE t0, t1, t2;
+#
+# BUG#12414917 - ISCLOSED() CRASHES ON 64-BIT BUILDS
+#
+SELECT ISCLOSED(CONVERT(CONCAT('     ', 0x2), BINARY(20)));
+ISCLOSED(CONVERT(CONCAT('     ', 0x2), BINARY(20)))
+NULL
 End of 5.1 tests

mysql-test/t/gis.test

@@ -812,4 +812,11 @@ CREATE TABLE t3 (
 # cleanup
 DROP TABLE t0, t1, t2;
 
+
+--echo #
+--echo # BUG#12414917 - ISCLOSED() CRASHES ON 64-BIT BUILDS
+--echo #
+SELECT ISCLOSED(CONVERT(CONCAT('     ', 0x2), BINARY(20)));
+
+
 --echo End of 5.1 tests

sql/spatial.cc

@@ -627,7 +627,8 @@ int Gis_line_string::is_closed(int *closed) const
     return 0;
   }
   data+= 4;
-  if (no_data(data, SIZEOF_STORED_DOUBLE * 2 * n_points))
+  if (n_points == 0 ||
+      no_data(data, SIZEOF_STORED_DOUBLE * 2 * n_points))
     return 1;
 
   /* Get first point */