Remove unnecessary nested conditions

Author: kgryte

lib/node_modules/@stdlib/stats/incr/mstdev/lib/main.js

@@ -130,9 +130,6 @@ function incrmstdev( W, mean ) {
 		// Case: initial window...
 		else if ( N < W ) {
 			buf[ i ] = x; // update buffer
-			if ( isnan( M2 ) ) {
-				return NaN;
-			}
 			N += 1;
 			delta = x - mu;
 			mu += delta / N;
@@ -210,9 +207,6 @@ function incrmstdev( W, mean ) {
 		// Case: initial window...
 		else if ( N < W ) {
 			buf[ i ] = x; // update buffer
-			if ( isnan( M2 ) ) {
-				return NaN;
-			}
 			N += 1;
 			delta = x - mu;
 			M2 += delta * delta;