fix crash when clipboard_pull_text returns null

Author: jacob1

build/readme.txt

@@ -673,9 +673,6 @@ Immediate TODO: '>' means currently being worked on/added next
 >add all missing lua functions
 move menu_count to Menus.h (needs tooltips done first)
 Finish brushes (change all instances of rx and ry to the brush things)
-redo GolTool as MultipleTool, special tools that can draw multiple forms of an element (maybe)
-Redo wall ID's and walls entirely
-Redo gmenu
 Redo fav menu ...
 Redo (Add) tooltips
 Add in all missing lua functions except for interface api

src/interface.cpp

@@ -712,7 +712,9 @@ void ui_edit_process(int mx, int my, int mb, int mbq, ui_edit *ed)
 			}
 			else if(sdl_mod & (KMOD_CTRL) && sdl_key=='v')//paste
 			{
-				char *paste = clipboard_pull_text();
+				char* paste = clipboard_pull_text();
+				if (!paste)
+					return;
 				int pl = strlen(paste);
 				if ((textwidth(str)+textwidth(paste) > ed->w-14 && !ed->multiline) || (pl+strlen(ed->str)>ed->limit) || (float)(((textwidth(str)+textwidth(paste))/(ed->w-14)*12) > ed->h && ed->multiline && ed->limit != 1023))
 					break;