fix dividing by zero (henrypp/memreduct#262 henrypp/memreduct#263)

-nan(ind) is not a way to display zero, it's a result of dividing by zero and this is a crash for int
check is only for virtual memory (its amount can be controlled by user)
physical memory can't be zero (then how you even run this)
not sure about system_cache

also optimized math for memory percentages
percent_f calculated first, then it converts to int percent

Author: XakerTwo

src/routine.c

@@ -9168,8 +9168,8 @@ NTSTATUS _r_sys_getmemoryinfo (
 
 		out_buffer->physical_memory.used_bytes = out_buffer->physical_memory.total_bytes - out_buffer->physical_memory.free_bytes;
 
-		out_buffer->physical_memory.percent = (ULONG)PR_CALC_PERCENTOF (out_buffer->physical_memory.used_bytes, out_buffer->physical_memory.total_bytes);
 		out_buffer->physical_memory.percent_f = PR_CALC_PERCENTOF (out_buffer->physical_memory.used_bytes, out_buffer->physical_memory.total_bytes);
+		out_buffer->physical_memory.percent = (ULONG)out_buffer->physical_memory.percent_f;
 	}
 
 	// file cache information
@@ -9181,8 +9181,8 @@ NTSTATUS _r_sys_getmemoryinfo (
 		out_buffer->system_cache.free_bytes = (ULONG64)sfci.PeakSize - (ULONG64)sfci.CurrentSize;
 		out_buffer->system_cache.used_bytes = sfci.CurrentSize;
 
-		out_buffer->system_cache.percent = (ULONG)PR_CALC_PERCENTOF (out_buffer->system_cache.used_bytes, out_buffer->system_cache.total_bytes);
 		out_buffer->system_cache.percent_f = PR_CALC_PERCENTOF (out_buffer->system_cache.used_bytes, out_buffer->system_cache.total_bytes);
+		out_buffer->system_cache.percent = (ULONG)out_buffer->system_cache.percent_f;
 	}
 
 	// page file information
@@ -9214,8 +9214,9 @@ NTSTATUS _r_sys_getmemoryinfo (
 			pagefile = pagefile->NextEntryOffset ? PTR_ADD_OFFSET (pagefile, pagefile->NextEntryOffset) : NULL;
 		}
 
-		out_buffer->page_file.percent = (ULONG)PR_CALC_PERCENTOF (out_buffer->page_file.used_bytes, out_buffer->page_file.total_bytes);
-		out_buffer->page_file.percent_f = PR_CALC_PERCENTOF (out_buffer->page_file.used_bytes, out_buffer->page_file.total_bytes);
+		//memory are zeroed at start - no need to reassign zero
+		if (out_buffer->page_file.total_bytes) out_buffer->page_file.percent_f = PR_CALC_PERCENTOF (out_buffer->page_file.used_bytes, out_buffer->page_file.total_bytes);
+		out_buffer->page_file.percent = (ULONG)out_buffer->page_file.percent_f;
 	}
 
 	_r_mem_free (pagefiles);