Empty qualifier cell should not be returned if it does not match QualifierFilter

hbase(main):002:0> put 'testTable','testrow','f:testcol1','testvalue1'
0 row(s) in 0.0040 seconds

hbase(main):003:0> put 'testTable','testrow','f:','testvalue2'
0 row(s) in 0.0070 seconds

# get row with empty column f:, result is correct.
hbase(main):004:0> scan 'testTable',{FILTER => "QualifierFilter (=, 'binary:')"}
ROW                                         COLUMN+CELL                                                                                                                    
 testrow                                    column=f:, timestamp=1536218563581, value=testvalue2                                                                           
1 row(s) in 0.0460 seconds

# get row with column f:testcol1, result is incorrect.
hbase(main):005:0> scan 'testTable',{FILTER => "QualifierFilter (=, 'binary:testcol1')"}
ROW                                         COLUMN+CELL                                                                                                                    
 testrow                                    column=f:, timestamp=1536218563581, value=testvalue2                                                                           
 testrow                                    column=f:testcol1, timestamp=1536218550827, value=testvalue1                                                                   
1 row(s) in 0.0070 seconds