Description of problem:
with almost default settings, I was writting BNF:

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
cmp_expr		:= cmp_expr_operand + cmp_expr_tail
cmp_expr_tail		:= '==' + 
			 | '!=' + 
			 | '>'  + 
			 | '>=' + 
			 | '<'  + 
			 | '<=' + 
			 | epsilon
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


The  content between <<<< and >>>> are the Fcontent in the buffer, please notice that:
1. the indents are tabs.
2. there is one space after '+' on each lineend

I did the following:
1. select the text "cmp_expr_operand" and copy in the register .
2. block select mode, select all of the spaces after '+' since line 2
3. press p to paste the word in block mode


vim crashes everytime, no matter gvim or in console.


Version-Release number of selected component:
vim-X11-7.4.475-2.fc21

Additional info:
reporter:       libreport-2.3.0
backtrace_rating: 4
cmdline:        vi syntax.txt
crash_function: vim_free
executable:     /usr/bin/gvim
kernel:         4.0.8-200.fc21.x86_64
runlevel:       N 5
type:           CCpp
uid:            1000

Truncated backtrace:
Thread no. 1 (8 frames)
 #36 vim_free at misc2.c:1741
 #37 ml_flush_line at memline.c:3525
 #38 ml_get_buf at memline.c:2499
 #39 ml_get at memline.c:2422
 #40 do_put at ops.c:3809
 #41 nv_put at normal.c:9366
 #42 normal_cmd at normal.c:1160
 #43 main_loop at main.c:1342